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Weight loss at high altitude: Pathophysiology and practical implications

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Abstract

Climbers at high altitude (>5000 m) lose weight. This impairs performance and safety, but the mechanisms are not entirely due to an imbalance between energy intake and expenditure. There is some evidence of carbohydrate malabsorption, but there are also changes in fat metabolism and total body water. This paper considers the physiological control of weight and then discusses the changes in each parameter before addressing the practical implications.

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... There is a decline in body mass in response to extended exposure to altitude or hypoxia (Benso et al., 2007;Hamad & Travis, 2006;Rose et al., 1988;Westerterp & Kayser, 2006;Westerterp-Plantenga et al., 1999;Zaccaria, Ermolao, Bonvicini, Travain, & Varnier, 2004). When ascending to a higher altitude, the barometric pressure exerted on oxygen is decreased causing a decline in arterial oxygen saturation (Mazzeo, 2008). ...
... When the body cannot deliver an adequate supply of oxygenated blood to target tissues due to high altitude, this causes a state of hypoxia. Many factors may contribute to reductions in body mass at altitude, including appetite, exercise (Westerterp & Kayser, 2006), altered intestinal function, and overall disruption of energy balance (Hamad & Travis, 2006;Tschöp & Morrison, 2001) resulting in changes to both fat mass and muscle mass (Tschöp & Morrison, 2001). ...
... During these short periods, the negative consequences associated with hypoxia such as a loss of appetite and body mass do not appear to be evident. Longer durations or more intense hypoxia may be required in order to see differences in appetite, appetite regulating hormones, and overall energy imbalances-which may lead to decreases in body mass (Hamad & Travis, 2006;Tschöp & Morrison, 2001;Westerterp & Kayser, 2006). When the current study is interpreted along with previous research it contributes to the understanding of the time course of responses associated with hypoxia and may be considered in interventions designed to counter the negative outcomes associated with hypoxia. ...
... This adaptive response is facilitated by stimulated erythropoiesis, increases in red cell mass as well as by further increases in ventilatory response to hypoxia (Baggish and Wolfel, 2014). In addition to these adaptations, hypoxic environments are frequently shown to influence a person's body composition (e.g., reductions in body weight, fat free mass (FFM), fat mass (FM), muscle mass (MM) and/or body water) (Hamad and Travis, 2006). ...
... Acute increases in BMR might also be explained by the stress of an initial energy deficit, whereas the decline in BMR during prolonged stays could depend, at least in part, on personal fitness, such that those with a higher fitness level will experience larger reductions in direction to baseline levels (Mawson et al., 2000). In addition to an increased BMR, at least at altitudes above 5000 m, a negative energy balance may result from a reduced energy intake due to either a reduced appetite (Westerterp-Plantenga et al., 1999) or, in part, by impaired intestinal function (Hamad and Travis, 2006). In order to negate loss of heat and maintain body temperature in cold environments, an additional increase in energy expenditure may arise due to involuntary shivering (nonshivering thermogenesis), which is activated to increase heat production and involves depletion of fat storages (Burtscher et al., 2018). ...
... In order to negate loss of heat and maintain body temperature in cold environments, an additional increase in energy expenditure may arise due to involuntary shivering (nonshivering thermogenesis), which is activated to increase heat production and involves depletion of fat storages (Burtscher et al., 2018). Moreover, increased energy expenditure during extensive high-altitude hiking could be responsible for a negative energy balance leading to changes in body composition (Westerterp et al., 1992;Hamad and Travis, 2006;Kayser and Verges, 2013). ...
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Changes in body composition and weight loss frequently occur when humans are exposed to hypoxic environments. The mechanisms thought to be responsible for these changes are increased energy expenditure resulting from increased basal metabolic rate and/or high levels of physical activity, inadequate energy intake, fluid loss as well as gastrointestinal malabsorption. The severity of hypoxia, the duration of exposure as well as the level of physical activity also seem to play crucial roles in the final outcome. On one hand, excessive weight loss in mountaineers exercising at high altitudes may affect performance and climbing success. On the other, hypoxic conditioning is presumed to have an important therapeutic potential in weight management programs in overweight/obese people, especially in combination with exercise. In this regard, it is important to define the hypoxia effect on both body composition and weight change. The purpose of this study is to define, through the use of meta-analysis, the extent of bodyweight -and body composition changes within the three internationally classified altitude levels (moderate altitude: 1500–3500 m; high altitude: 3500–5300 m; extreme altitude: >5300 m), with emphasis on physical activity, nutrition, duration of stay and type of exposure.
... Les individus qui effectuent un séjour prolongé en hypoxie perdent généralement du poids, de la masse grasse, mais aussi de la masse maigre (13,14). La réalisation d'efforts prolongés et répétés peut contribuer au déséquilibre énergétique responsable de ces modifications. ...
... Toutefois, lors d'expéditions en altitude, la DE, mesurée par la méthode de l'eau doublement marquée, demeure modeste (~2,3 fois la DE de repos) et le déficit énergétique (~1 350 kcal.j -1 ) est dû à la réduction de l'ingestion alimentaire (15) sans modification de l'absorption intestinale (14). Une réduction de l'ingestion alimentaire est d'ailleurs observée en altitude ou en chambre hypobare (13), même si les sujets sont peu ou pas actifs. ...
... Une réduction de l'ingestion alimentaire est d'ailleurs observée en altitude ou en chambre hypobare (13), même si les sujets sont peu ou pas actifs. Ceci semble dû à la précarité des conditions de vie, au manque de sommeil, à l'isolement, et à la difficulté d'emporter et de préparer une nourriture variée et appétissante, mais aussi à un effet anorexigène de l'hypoxie (14). Les mécanismes précis de cette réduction de et la sueur (20) ou l'utilisation de traceurs isotopiques (21). ...
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Chez un jeune adulte masculin, la dépense énergétique (DE) de repos est de ∼1,2 kcal.min−1 (∼1 750 kcal.j−1: puissance ∼85 W, pour 70 kg et ∼1,85 m2 de surface corporelle; 1 W=1 J.s−1 et 1 kcal =4,2 kJ). Dans les pays développés, la plupart des individus font peu ďexercises en dehors de ceux nécessaires à la vie courante, et la DE exprimée en multiple de la DE de repos (PAL, pour physical activity level: rapport DE/DE de repos) varie de ∼1,2 à ∼1,9 selon ľemploi, du sujet (1).
... Recent interest in studying higher protein, moderate carbohydrate diets at HA (59) has been driven by the knowledge that unintentional fat-free mass loss is common during HA sojourn (33,78), and that higher protein diets preserve fat-free mass during weight loss at SL (60,81). However, the effects of these diets on host-gut microbiota dynamics at HA are unknown. ...
... During HA, participants were under constant supervision, consumed a controlled and measured diet, and engaged in prescribed physical activity. Diets contained either a standard or higher amount of protein, and were designed to induce weight loss, which is common during HA sojourn (33). The estimated energy deficit at HA was 70% or 1,849 kcal/day (SD 511) (9). ...
... The latter observation implies that sustained hypoxia per se is likely not the mechanism underpinning observed changes in relative abun-dance and that some combination of hypobaria, hypoxia, weight loss, increased physical activity, and dietary change is responsible. Of note, all of these factors are inevitable or common during HA sojourn (33). ...
Article
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Hypobaric hypoxia, and dietary protein and fat intakes have been independently associated with an altered gastrointestinal (GI) environment and gut microbiota, but little is known regarding host-gut microbiota interactions at high altitude (HA) and the impact of diet macronutrient composition. This study aimed to determine the effect dietary protein:fat ratio manipulation on the gut microbiota and GI barrier function during weight loss at high altitude (HA), and to identify associations between the gut microbiota and host responses to HA. Following sea level (SL) testing, 17 healthy males were transported to HA (4300m) and randomly assigned to consume provided standard-protein (SP; 1.1g/kg/d, 39% fat) or higher-protein (HP; 2.1g/kg/d, 23% fat) carbohydrate-matched hypocaloric diets for 22d. Fecal microbiota composition and metabolites, GI barrier function, GI symptoms, and acute mountain sickness (AMS) severity were measured. Macronutrient intake did not impact fecal microbiota composition, had only transient effects on microbiota metabolites, and had no effect on increases in small intestinal permeability, GI symptoms, and inflammation observed at HA. AMS severity was also unaffected by diet, but in exploratory analyses was associated with higher SL relative abundance of Prevotella, a known driver of inter-individual variability in human gut microbiota composition, and greater microbiota diversity after AMS onset. Findings suggest that the gut microbiota may contribute to variability in host responses to HA independent of the dietary protein:fat ratio, but should be considered preliminary and hypothesis-generating due to the small sample size and exploratory nature of analyses associating the fecal microbiota and host responses to HA.
... 27% (Butterfield et al., 1992), and decrease mass, body mass index, and cardio-metabolic risk factors in obese populations (Kayser & Verges, 2013;Lippl et al., 2010;Wee & Climstein, 2015) which may be related to cold exposure (Nair et al., 1971), appetite regulation, hormone secretion and neurotransmitters involved in energy balance and weight control (Hamad & Travis, 2006). Altitude exposure is a popular method of training for endurance athletes in pursuit of improved performance at sea level (Saunders et al., 2009), but training blocks routinely occur at moderate elevations (Bärtsch & Saltin, 2008) between 2000-3000m. ...
... The present experimental group were living and training at moderate altitude; however, with a mean environmental temperature of approximately 20 °C, an increase in energy expenditure due to nonexercise activity thermogenesis (shivering) is unlikely. Other potential influences on metabolic rate, particularly at high altitude, include improved mitochondrial oxidative capacity (Larsen et al., 2011), sympathetic nervous system activity (Grover et al., 1986) and thyroid activity (Hamad & Travis, 2006). In addition, a number of hormones and cytokines may impact the body's function at high altitude. ...
... In addition, a number of hormones and cytokines may impact the body's function at high altitude. Specifically, leptin is known to influence the hypothalamic regulation of food intake, and is reported to increase at altitude (Hamad & Travis, 2006), resulting in weight loss and diminished appetite. The present group of athletes did not appear to change their dietary intake during their sojourn to moderate altitude; however, we were only able to obtain 6 out of a possible 10 food diaries so the small sample makes it difficult to draw statistically meaningful conclusions. ...
Article
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High altitude exposure can increase resting metabolic rate (RMR) and induce weight loss in obese populations, but there is a lack of research regarding RMR in athletes at moderate elevations common to endurance training camps. The present study aimed to determine whether four weeks of classical altitude training affects RMR in middle-distance runners. Ten highly-trained athletes were recruited for four weeks of endurance training undertaking identical programs at either 2200m in Flagstaff, Arizona (ALT, n=5) or 600m in Canberra, Australia (CON, n=5). RMR, anthropometry, energy intake, and haemoglobin mass (Hbmass) were assessed pre- and post-training. Weekly run distance during the training block was: ALT 96.8±18.3km; CON 103.1±5.6km. A significant interaction for Time*Group was observed for absolute (kJ.day-1) (F-statistic, p-value: F(1,8)=13.890, p=0.01) and relative RMR (F(1,8)=653.453, p=0.003) POST-training. No significant changes in anthropometry were observed in either group. Energy intake was unchanged (mean ± SD of difference ALT: 195±3921kJ, p=0.25; CON: 836±7535kJ, p=0.75). A significant main effect for time was demonstrated for total Hbmass (g) (F(1,8)=13.380, p=0.01), but no significant interactions were observed for either variable [Total Hbmass (g): F(1,8)=1.706, p=0.23; Relative Hbmass (g.kg-1): F(1,8)=0.609, p=0.46]. These novel findings have important practical application to endurance athletes routinely training at moderate altitude, and those seeking to optimize energy management without compromising training adaptation. Altitude exposure may increase RMR and enhance training adaptation,. During training camps at moderate altitude, an increased energy intake is likely required to support an increased RMR and provide sufficient energy for training and performance.
... Weight loss has been widely reported in hypoxic chamber experiments and after sojourns at high altitude, with associations between magnitude of loss and both duration of exposure to hypoxia and level of hypoxemia [5][6][7]. Current evidence seems to point to an alteration of appetite control and consequent reduction of energy intake as a determinant of the weight loss, whereas energy expenditure (resting and dietary induced thermogenesis) seems to be less affected [8]. More than 60% of the weight lost is typically composed of FFM leading to a decline of muscle contractility and physical performance and, consequently, an individual's capacity to cope with extreme environmental conditions [9]. ...
... Data from previous studies have shown that the extent and rate of weight loss is correlated with the rate, extent and duration of the exposure to hypoxia [5,6,[32][33][34], but the factors involved in the onset and maintenance of this remain undetermined. Variability in the magnitude of weight loss in the face of a consistent exposure (rate, extent and duration) to hypobaric hypoxia in our participants is striking and consistent with previous reports [5][6][7]34]. ...
... Data from previous studies have shown that the extent and rate of weight loss is correlated with the rate, extent and duration of the exposure to hypoxia [5,6,[32][33][34], but the factors involved in the onset and maintenance of this remain undetermined. Variability in the magnitude of weight loss in the face of a consistent exposure (rate, extent and duration) to hypobaric hypoxia in our participants is striking and consistent with previous reports [5][6][7]34]. This variability in response to a consistent stimulus provided the signal on which our analysis is based. ...
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Objectives: Sarcopenia refers to the involuntary loss of skeletal muscle and is a predictor of physical disability/mortality. Its pathogenesis is poorly understood, although roles for altered hypoxic signaling, oxidative stress, adipokines and inflammatory mediators have been suggested. Sarcopenia also occurs upon exposure to the hypoxia of high altitude. Using data from the Caudwell Xtreme Everest expedition we therefore sought to analyze the extent of hypoxia-induced body composition changes and identify putative pathways associated with fat-free mass (FFM) and fat mass (FM) loss. Methods: After baseline testing in London (75 m), 24 investigators ascended from Kathmandu (1300 m) to Everest base camp (EBC 5300 m) over 13 days. Fourteen investigators climbed above EBC, eight of whom reached the summit (8848 m). Assessments were conducted at baseline, during ascent and after one, six and eight week(s) of arrival at EBC. Changes in body composition (FM, FFM, total body water, intra- and extra-cellular water) were measured by bioelectrical impedance. Biomarkers of nitric oxide and oxidative stress were measured together with adipokines, inflammatory, metabolic and vascular markers. Results: Participants lost a substantial, but variable, amount of body weight (7.3±4.9 kg by expedition end; p
... L owlanders sojourning at high altitude (HA; 2500-5000 m) commonly experience unintentional weight loss (Westerterp and Kayser, 2006;Pasiakos et al., 2017). The etiology is multifactorial, but reduced energy intake is a contributing factor (Hamad and Travis, 2006;Westerterp and Kayser, 2006), and coincides with a loss of appetite putatively characterized by a rapid reduction in hunger during meals and early satiation (Westerterp-Plantenga et al., 1999). Some evidence suggests that this HA anorexia may be related to hypoxia-induced increases in the anorexigenic hormones, leptin (Tschop et al., 1998;Shukla et al., 2005;Barnholt et al., 2006;Sierra-Johnson et al., 2008;Snyder et al., 2008) and cholecystokinin (CCK) (Bailey et al., 2000), and suppression of the orexigenic hormone ghrelin (Shukla et al., 2005;Riepl et al., 2012;Wasse et al., 2012;Matu et al., 2017aMatu et al., , 2017b. ...
... However, findings are not consistent across all studies (Zaccaria et al., 2004;Benso et al., 2007;Vats et al., 2007;Riepl et al., 2012;Aeberli et al., 2013;Debevec et al., 2014Debevec et al., , 2016Mekjavic et al., 2016;Morishima and Goto, 2016). These inconsistencies and heterogeneous study designs have impeded reaching consensus on the role of appetitemediating hormones in the development and persistence of HA anorexia (Hamad and Travis, 2006;Westerterp and Kayser, 2006;Raff et al., 2008;Sierra-Johnson et al., 2008;Debevec, 2017). An improved understanding of the contribution of appetite-mediating hormones to HA anorexia, and how that impact evolves with acclimatization, could help develop optimized strategies for mitigating HA anorexia. ...
... These effects may be potentiated at HA due to the higher thermogenic effect of protein relative to fat (Veldhorst et al., 2008) which could worsen hypoxia by increasing postprandial oxygen consumption (Westerterp and Kayser, 2006;Veldhorst et al., 2008). Higher protein diets may also be incompatible with food preferences at HA, which have favored carbohydrate in some (Boyer and Blume, 1984;Kayser et al., 1993;Westerterp-Plantenga et al., 1999;Bailey et al., 2004;Hamad and Travis, 2006;Matu et al., 2017aMatu et al., , 2017b, but not all (Rose et al., 1988;Reynolds et al., 1998;Aeberli et al., 2013), studies. Collectively, these effects could prove counterproductive to retaining fat-free mass during HA-induced weight loss by exacerbating HA anorexia and further reducing energy intake. ...
Article
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Karl, J. Philip, Renee E. Cole, Claire E. Berryman, Graham Finlayson, Patrick N. Radcliffe, Matthew T. Kominsky, Nancy E. Murphy, John W. Carbone, Jennifer C. Rood, Andrew J. Young, and Stefan M. Pasiakos. Appetite Suppression and Altered Food Preferences Coincide with Changes in Appetite-Mediating Hormones During Energy Deficit at High Altitude, But Are Not Affected by Protein Intake. High Alt Med Biol. 00:000-000, 2018.-Anorexia and unintentional body weight loss are common during high altitude (HA) sojourn, but underlying mechanisms are not fully characterized, and the impact of dietary macronutrient composition on appetite regulation at HA is unknown. This study aimed to determine the effects of a hypocaloric higher protein diet on perceived appetite and food preferences during HA sojourn and to examine longitudinal changes in perceived appetite, appetite mediating hormones, and food preferences during acclimatization and weight loss at HA. Following a 21-day level (SL) period, 17 unacclimatized males ascended to and resided at HA (4300 m) for 22 days. At HA, participants were randomized to consume measured standard-protein (1.0 g protein/kg/d) or higher protein (2.0 g/kg/d) hypocaloric diets (45% carbohydrate, 30% energy restriction) and engaged in prescribed physical activity to induce an estimated 40% energy deficit. Appetite, food preferences, and appetite-mediating hormones were measured at SL and at the beginning and end of HA. Diet composition had no effect on any outcome. Relative to SL, appetite was lower during acute HA (days 0 and 1), but not different after acclimatization and weight loss (HA day 18), and food preferences indicated an increased preference for sweet- and low-protein foods during acute HA, but for high-fat foods after acclimatization and weight loss. Insulin, leptin, and cholecystokinin concentrations were elevated during acute HA, but not after acclimatization and weight loss, whereas acylated ghrelin concentrations were suppressed throughout HA. Findings suggest that appetite suppression and altered food preferences coincide with changes in appetite-mediating hormones during energy deficit at HA. Although dietary protein intake did not impact appetite, the possible incongruence with food preferences at HA warrants consideration when developing nutritional strategies for HA sojourn.
... Many authors in recent decades have highlighted the effects of high altitude on nutritional status, metabolism and body composition [8][9][10][11][12][13][14]. Based on these literature reviews, it can be said that there is a shred of evidence that altitude exposure leads to many physiological challenges such as weight loss-in particular of fat free mass [15] and decreased liquid intake-caused by changes of diet and habits and to a metabolic effect elicited by hypobaric hypoxia. The physiology behind weight loss at altitude is constituted by several factors, from an imbalance between intake and expenditure to loss of appetite, changes in body composition and dehydration [15]. ...
... Based on these literature reviews, it can be said that there is a shred of evidence that altitude exposure leads to many physiological challenges such as weight loss-in particular of fat free mass [15] and decreased liquid intake-caused by changes of diet and habits and to a metabolic effect elicited by hypobaric hypoxia. The physiology behind weight loss at altitude is constituted by several factors, from an imbalance between intake and expenditure to loss of appetite, changes in body composition and dehydration [15]. Muscular distress provoked by a physical effort at high altitude affects body composition and activates pro-inflammatory pathways [16]. ...
... The amount of weight loss during mountain travelling is dependent on the amount of duration and altitude exposure [15]. It has been recently reported that a reduction of body weight, body fat and waist circumference occurs after a prolonged sojourn (22 days) at high altitude [16]. ...
Article
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High-altitude exposure leads to many physiological challenges, such as weight loss and dehydration. However, little attention has been posed to the role of nutrition and ethnic differences. Aiming to fulfill this gap, five Italian trekkers and seven Nepalese porters, all males, recorded their diet in diaries during a Himalayan expedition (19 days), and the average daily intake of micro and macro-nutrients were calculated. Bioimpedance analysis was performed five times during the trek; muscle ultrasound was performed before and after the expedition, only for the Italians. The Nepalese group consumed a lot of rice and only Italians consumed cheese. Water intake was slightly over 3000 g/d for both groups. Nepalese diet had a higher density of dietary fibre and lower density of riboflavin, vitamins A, K, and B12. Intake of calcium was lower than recommended levels. Body mass index, waist circumference, fat-free mass, and total body water decreased in both groups, whereas resistance (Rz) increased. Italians reactance (Xc) increased at day 9, whereas that of Nepalese occurred at days 5, 9, and 16. The cross-sectional area of the Vastus lateralis was reduced after the expedition. Specific nutritional and food-related risk factors guidance is needed for diverse expedition groups. Loss of muscle mass and balance of fluids both deserve a particular focus as concerns altitude expeditions.
... This seems to be greatly dependent on the duration of hypoxic exposure and accounts for a greater weight loss in the first weeks of altitude sojourns [17,18]. The time, duration and dose factors of this mechanism and its implications for an adapted nutrition for altitude sojourns in the human metabolism are not completely understood [19]. Research at a cellular level on isolated human adipocytes in their reaction to hypoxia most often concentrates on HIF-mediated inflammatory signaling in a long-term hypoxic state in regard to obesity, cancer or cardiovascular diseases [20][21][22][23]. ...
... Especially during prolonged exposures, an imbalance of energy expenditure and energy intake causes a depletion of body fat stores. This misbalance seems to increase with increasing altitude [19]. De Glieszinski et al. investigated the effect of prolonged hypoxia on adipose tissue lipolysis during a stay in a hypobaric altitude laboratory. ...
Article
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Several publications and random observations have reported weight loss in high-altitude sojourners of both sexes. This could be a result of multiple adaptations, which hypoxia and mountaineering provoke on a cellular and organic level. Several publications have discussed the effect on appetite-regulating hormones to be one of the main contributing factors. We aimed to review the available data and show the current state of knowledge regarding nutritional aspects in high altitude with a special focus on fatty dietary forms. To reach this aim we conducted a literature search via PubMed according to the PRISMA 2020 protocol to identify relevant studies. We found that very few studies cover this field with scientifically satisfying evidence. For final analysis, reviews as well as papers that were not clearly related to the topic were excluded. Six articles were included discussing hormonal influences and the impact of exercise on appetite regulation as well as genetic factors altering metabolic processes at altitude. Leptin expression seems to be the biggest contributor to appetite reduction at altitude with an initial increase followed by a decrease in the course of time at high altitude. Its expression is greatly dependent on the amount of white adipose tissue. Since the expression of leptin is associated with an increased β-oxidation of fatty acids, a high-fat diet could be advantageous at a certain time point in the course of high-altitude sojourns.
... reductions in body weight, fat-free mass, fat mass, muscle mass, and/or body water) (2)(3)(4). Weight loss has been widely reported in hypoxic chamber experiments and after sojourns at high altitudes (5)(6)(7). Some studies have found that skeletal muscle mass decreased with increasing altitude as the hypoxic environment accelerated the decomposition of skeletal muscle and inhibited protein synthesis (8,9). ...
... Bodyweight reduction is an inevitable consequence of chronic hypoxic exposure (5). In our study, people living at higher altitude were found to have lower BMI, consistent with the study of Ye et al. (8). ...
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Background and Purpose A high-altitude environment was known to have a negative effect on bone and lead to a higher incidence of hip fracture. However, the dependence of muscle composition on altitude is unclear. Thus, we aimed to compare muscle density and area in plateau and low altitude area and to determine the effect of the altitude on these outcomes. Methods Community dwelling adults over 60 years old living in Beijing (elevation 50 m; 300 subjects,107 men and 193 women) or Kunming (elevation 2000 m; 218 subjects,83 men and 135 women) for more than 10 years were enrolled. Quantitative CT was performed in all subjects and cross-sectional area and attenuation measured in Hounsfield units (HU) were determined for the trunk, gluteus, and mid-thigh muscles. Results Compared to Beijing, Kunming adults were slimmer (Beijing men vs Kunming men: 25.08 ± 2.62 vs 23.94 ± 3.10kg/m ² , P =0.013; Beijing women vs Kunming women: 25.31 ± 3.1 vs 23.98 ± 3.54 kg/m ² , P = 0.001) and had higher muscle density in the L2-trunk and gluteus maximus muscles after adjustment for age and BMI (L2-trunk muscles: Beijing men 29.99 ± 4.17 HU vs Kunming men 37.35 ± 4.25 HU, P < 0.0001; Beijing women 27.37 ± 3.76 HU vs Kunming women 31.51 ± 5.12 HU, P < 0.0001; Gluteus maximus muscle: Beijing men 35.11 ± 6.54 HU vs Kunming men 39.36 ± 4.39 HU, P = 0.0009; Beijing women 31.47 ± 6.26 HU vs Kunming women 34.20 ± 5.87 HU P =0.0375). Age was similar in both cohorts and no differences were observed in the gluteus medius and minimus muscle or the mid-thigh muscle, either in the area or density. Conclusions Compared with Beijing, the adults in Kunming had higher muscle density of the gluteus maximus and L2 trunk muscles, showing that living at a higher altitude might be beneficial to muscle quality.
... It has been suggested that humans cannot maintain weight above 16,405 ft (5000 m) and that the magnitude of weight loss is dependent on the amount of time spent at high altitude. 1 This case report he also has weight loss 3 kg (4.4%) after descended Mt Everest same as the results from the previous study are consistent with that theory as the climber lost weight. The loss of 7% of body mass following the Everest expedition is identical to what has been reported for other Everest climbers. ...
... It is likely a combination of increased exertion, decreased appetite, increases in leptin concentrations, leptin is a key role hormone involved in neuroendocrine regulation of energy by reduced appetite and also increase basal metabolic rate, intestinal dysfunction there is malabsoption of food or change in intestinal permeability. 1 Ward et al. 2 noted that weight loss within the first 3 week of an expedition is typical due to a change from a semi-sedentary lifestyle to one that involves trekking long distances. However, more research is needed to determine what influence hypoxia has on weight loss independent of physical exertion. ...
... Although "nutrition at altitude" has been commonly reviewed [9][10][11][12][13][14][15], the vast majority of nutrition recommendations are based on research conducted at high to extreme altitudes, which do not correspond to the training altitudes typical of elite athletes (~ 1600-2400 m). However, recently, several new publications on nutrition interventions at low-moderate altitudes have emerged. ...
... Do athletes need to appreciably increase dietary CHO and/or CHO fueling during training sessions at low-moderate altitudes? [9][10][11][12][13][14][15] Increased oxidative stress and anti-oxidant requirements Is there an appreciable increase in RONS at low-moderate altitudes that is linked to injury/illness and/or altitude-induced adaptation? ...
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Training at low to moderate altitudes (~ 1600-2400 m) is a common approach used by endurance athletes to provide a distinctive environmental stressor to augment training stimulus in the anticipation of increasing subsequent altitude- and sea-level-based performance. Despite some scientific progress being made on the impact of various nutrition-related changes in physiology and associated interventions at mountaineering altitudes (> 3000 m), the impact of nutrition and/or supplements on further optimization of these hypoxic adaptations at low-moderate altitudes is only an emerging topic. Within this narrative review we have highlighted six major themes involving nutrition: altered energy availability, iron, carbohydrate, hydration, antioxidant requirements and various performance supplements. Of these issues, emerging data suggest that particular attention be given to the potential risk for poor energy availability and increased iron requirements at the altitudes typical of elite athlete training (~ 1600-2400 m) to interfere with optimal adaptations. Furthermore, the safest way to address the possible increase in oxidative stress associated with altitude exposure is via the consumption of antioxidant-rich foods rather than high-dose antioxidant supplements. Meanwhile, many other important questions regarding nutrition and altitude training remain to be answered. At the elite level of sport where the differences between winning and losing are incredibly small, the strategic use of nutritional interventions to enhance the adaptations to altitude training provides an important consideration in the search for optimal performance.
... Also, exposure to reduced levels of inspired oxygen (hypoxia) negatively influences energy balance, something originally observed during prolonged high-altitude climbing expeditions, but now also documented in more controlled conditions such as hypobaric chambers and normobaric hypoxia environments (rooms, tents, etc.). [2][3][4][5] One reason for a continued interest in hypoxia as a modulator of energy balance is the still steadily increasing prevalence of obesity (i.e., excess body fat) worldwide, together with its comorbidities and associated heavy health burden. 6 Body mass index (BMI; weight/ height 2 in kg/m 2 ) is generally used as a-albeit imperfect-proxy for body composition. ...
... 5,72 There are changes in gut function affecting, for example, intestinal sugar transport, but these changes have no major impact on overall energy digestibility. 3,5,73 Direct measurements of food energy digestibility, involving bomb calorimetry of feces, yielded normal digestibility levels between 85% and 96% up to 8000 m. 5 Intestinal flora changes accompanied by diarrhea during a mountaineering expedition to the Himalayas might explain occasional malabsorption. 74 At lower potentially therapeutic altitudes, there is likely no malabsorption. ...
Article
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Because of the enduring rise in the prevalence of obesity worldwide, there is continued interest in hypoxia as a mechanism underlying the pathophysiology of obesity and its comorbidities and as a potential therapeutic adjunct for the management of the disease. Lifelong exposure to altitude is accompanied by a lower risk for obesity, whereas altitude sojourns are generally associated with a loss of body mass. A negative energy balance upon exposure to hypoxia can be due to a combination of changes in determinants of energy expenditure (resting metabolic rate and physical activity energy expenditure) and energy intake (appetite). Over the past 15 years, the potential therapeutic interest of hypobaric or normobaric hypoxic exposure in individuals with obesity—to lower body mass and improve health status—has become an active field of research. Various protocols have been implemented, using actual altitude sojourns or intermittent normobaric hypoxic exposures, at rest or in association with physical activity. Although several studies suggest benefits on body mass and cardiovascular and metabolic variables, further investigations are required before recommending hypoxic exposure in obesity management programs. Future studies should also better clarify the effects of hypoxia on appetite, the intestinal microbiota, and finally on overall energy balance.
... We have not found in existing scientific bibliography works of the evolution of this parameter after extreme altitude expeditions. Oelz Kinanthropometry at extreme altitude has traditionally been focused in body changes produced during expeditions, analysing the data collected immediately before and immediately after [27,33,34,[70][71][72][73]. In the present study, SISF, ABSF and the ∑6SF presented changes after expedition [SISF PRE (7.4±0.6 mm)/OFF (8.5±0.8 mm) vs. POST* (8.0±0.9 mm), ABSF PRE (5.2±0.4 mm)/ OFF (5.5±0.4 mm) vs. POST* (6±0.3 mm) and ∑6SF PRE (29.7±1.0 mm)/OFF (31.6±2.3 mm) vs. POST* (31.3±1.4 mm). ...
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Extreme Altitude (EA) and himalayism in its alpine style became a study subject in recent years from the point of view of physiology and cineanthropometry usually these studies are carried out only on expeditions with no monitoring within the time, and less on elite himalayist or successful high altitude climbers. There are no scientific studies based on longitudinal studies neither at sea level (SL) or on international elite climbers whom attempt to climb the highest mountains. Purpose: To analyze the evolution and correlation between physiological and cineanthropometric parameters in an elite male himalayist climber at SL before, after and off climbing expeditions during the period while our mountaineer has climbed the last four "eigh- thousanders" and all of them without supplementary oxygen. Methodology: Our climber has been subjected to cineanthropometric measurement (weight, six skinfolds, sum of them, body mass index and body fat percentage) and to an effort test on a treadmill (staged, progressive, intervallic and maximal) in order to take the physiological data (VO2max, HR, LA and RQ) before, during and off expedition at SL. Results: Analyzed data presented no significant (p<0.05) changes in our climber within the time nor on the moment of the season (after, before and off expedition) but we have found some significant (p<0.05) and very significant (p<0.01) intra variable and inter variable correlations. Conclusion: The outstanding form of our climber combined with his gift for acclimatization in part due to a broad climbing career ensures that he does not suffer any kind of significant alterations in the analyzed parameters according to the scientific literature. Our subject does not suffer either, against the majority of scientific literature, changes in his body composition. On the other hand the correlation of analyzed parameters coincides with the classical physiological studies.
... 5,10 Various mechanisms for the beneficial effects of hypoxic therapy have been shown, such as appetite suppression, enhanced ability to transport oxygen to working muscle and improvement of fat oxidation. 12,13 In addition, exercise in hypoxia imposes less stress on the locomotor systems, while resulting in similar physiological stress. 14 Therefore, hypoxic therapy is a promising modality for successful health promotion in the older obese population. ...
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Aim The aim of the present study was to examine the effect of exercise intervention in hypoxia as a novel treatment method for obesity in older men. Methods A total of 24 obese 65–70‐year‐old Korean men (66.5 ± 0.8 years) were randomly assigned to undergo hypoxic training (n = 12) or normoxic training (n = 12), and all participants carried out an exercise intervention composed of aerobic exercise on a treadmill (30 min) and bicycle (30 min), and resistance exercise (30–40 min) in normoxia, and 3000‐m normobaric hypoxia separately for a total of 12 weeks, three times a week. Health‐related dependent variables (body composition, physical fitness, pulmonary function and heart rate variability) were evaluated at pre‐ and post‐exercise intervention. Results Hypoxic training showed more improved body composition (bodyweight −5.68 vs −3.16 kg, %body fat −5.50 vs −1.97%, fat‐free mass 2.09 vs 1.06 kg), physical fitness (chair sit‐to‐stand 5.67 vs 4.58, pegboard 3.58 vs 2.17, tandem test −1.74 vs −1.31 s, one leg standing 6.27 vs 3.71 s), pulmonary function (forced vital capacity 0.15 vs 0.02 L, forced expiratory volume in 1 s 0.23 vs 0.01 L, percent of forced expiratory volume in 1 s 0.87 vs 0.08, maximal voluntary ventilation 5.26 vs 2.22 L) and heart rate variability (high frequency 0.94 vs 0.19 ms², low frequency/high frequency −0.28 vs −0.08, salivary cortisol −0.13 vs −0.04 μg/dL) than normoxic training. Conclusions Compared with normoxic training, hypoxic training is a novel and successful health promotion method in obese older populations. Geriatr Gerontol Int 2019; ••: ••–••.
... 1,16 Also, the increased oxygen delivering capacity of the blood is positively correlated with basal metabolic rate, and the enhanced oxygen transporting ability to working muscle by natural high altitude or artificial hypoxic condition contributes to improvement of fat oxidation and the reduction of body fat. [17][18][19][20] Several previous studies have investigated the therapeutic benefits of exposure or exercise in vari-ous altitude or hypoxic conditions in obese patients. 1,7,16,18,[21][22][23][24][25] Therefore, this review summarizes recent evidence suggesting that exposure or exercise training under hypoxic conditions might be a valuable and viable obesity therapeutic modality. ...
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Obesity is an important health problem caused by positive energy balance. Generally, low calorie dietary intake combined with regular exercise is the most common modality to lose bodily fat in obese people. Although this is the first modality of choice for obesity treatment, it needs to be applied to obese patients for at least 12 weeks or more and it does not provide consistent results because it is difficult to suppress increased appetite due to exercise. Recently, many researchers have been applying hypoxic conditions for the treatment of obesity, as many studies show that people residing in high altitudes have a lower percentage of body fat and fewer obesity-related illnesses than people living at sea level. Hypoxic therapy treatment, including hypoxic exposure or hypoxic exercise training, is recommended as a way to treat and prevent obesity by suppression of appetite, increasing basal metabolic rate and fat oxidation, and minimizing side effects. Hypoxic therapy inhibits energy intake and appetite-related hormones, and enhances various cardiovascular and metabolic function parameters. These observations indicate that hypoxic therapy is a new treatment modality for inducing fat reduction and promoting metabolic and cardiovascular health, which may be an important and necessary strategy for the treatment of obesity. As such, hypoxic therapy is now used as a general medical practice for obesity treatment in many developed countries. Therefore, hypoxic therapy could be a new, practical, and useful therapeutic modality for obesity and obesity-related comorbidities.
... The reasons for the reduction in lean body mass include the energy deficit under hypoxic conditions [46], duration of exposure [47], and the energy expenditure during exercise [48]. In our view, this reduction may also be related to the decrease in the irisin and 25-Hydroxyvitamin D levels, since both irisin and 1,25(OH) 2 D, which is the hydroxylated metabolite of 25 (OH)D, affect muscle regeneration by modulating energy processes [18,22,49]. ...
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Exposure to high-altitude hypoxia causes physiological and metabolic adaptive changes by disturbing homeostasis. Hypoxia-related changes in skeletal muscle affect the closely interconnected energy and regeneration processes. The balance between protein synthesis and degradation in the skeletal muscle is regulated by several molecules such as myostatin, cytokines, vitamin D, and irisin. This study investigates changes in irisin and myostatin levels in male climbers after a 2-week high-altitude expedition, and their association with 25(OH)D and indices of inflammatory processes. The study was performed in 8 men aged between 23 and 31 years, who participated in a 2-week climbing expedition in the Alps. The measurements of body composition and serum concentrations of irisin, myostatin, 25(OH)D, interleukin-6, myoglobin, high-sensitivity C-reactive protein, osteoprotegerin, and high-sensitivity soluble receptor activator of NF-κB ligand (sRANKL) were performed before and after expedition. A 2-week exposure to hypobaric hypoxia caused significant decrease in body mass, body mass index (BMI), free fat mass and irisin, 25-Hydroxyvitamin D levels. On the other hand, significant increase in the levels of myoglobin, high-sensitivity C-reactive protein, interleukin-6, and osteoprotegerin were noted. The observed correlations of irisin with 25(OH)D levels, as well as myostatin levels with inflammatory markers and the OPG/RANKL ratio indicate that these myokines may be involved in the energy-related processes and skeletal muscle regeneration in response to 2-week exposure to hypobaric hypoxia.
... Средња телесна маса иранских алпиниста износила је 74.51 kg, што је више од оне коју су навели Барбиери и сарадници (Barbieri, et al., 2012). Алпинисти се нису показали способним да одрже своју телесну масу на надморским висинама већим од 5.000 m (Hamad & Travis, 2006;Tschöp & Мorrison, 2001;Wagner, 2010). Кајзер и сарадници су открили смањење од 3% у телесној маси на надморским висинама изнад 5.000 m (Kayser, Acheson, Decombaz, Fern, & Cerretelli, 1992). ...
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The purpose of this study was to examine the anthropometric, physiological and physical traits of elite mountain climbers and relationship of these traits to success in mountain climbing. Thirty-eight elite male Iranian mountain climbers (height of 178.68 ± 5.77 cm, body mass index of 23.4 ± 2.78 kg/m 2 and age of 31.26 ± 6.93 years) were assessed for some anthropometric, physiological and physical variables. So that, height, weight, and also length and circumference of limbs were measured. Percent body fat was determined by 3 sites measurements of skin-folds thickness. Aerobic power was assessed via a 12-minute run, anaerobic power was determined using anaerobic step test, Vertical and horizontal jump performance were evaluated with Sargent jump and standing long jump tests respectively, 40 yard dash was used to assess speed, and muscular endurance of torso and upper body were evaluated using sit-ups and push-ups tests. The sum of scores related to sport achievements was considered as the criterion evaluating success of mountain climbers. Anthropometric traits (only age and percent body fat) showed a poor positive relationship (p<0.05) with success. Whilst there were relatively strong relationship between physiological and physical traits including aerobic power (p<0.01), an-aerobic power (p<0.01), vertical jump (p<0.05), lower body strength (p<0.01) and muscular endurance of torso (p<0.05) and upper body (p<0.01) with success of mountain climbers. Results indicate the importance of physiological and physical traits compared to anthropometric traits of mountain climbers and successful climbing depends largely on aforementioned characteristics.
... A large study found regional differences in BMI upon preliminary examination of statelevel US maps published by the Centers for Disease Control and Prevention (15). Obesity prevalence was inversely associated with elevation (16). The discovery of hypoxia inducible factor 1 (HIF1), a transcription factor, has been a breakthrough in the understanding of adaption to high altitudes (17,18). ...
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Objective: to explore changes in lipid levels in two groups of children of different ethnicities who were able to access vitamin D supplementation versus those who were not. Methods: A prospective one-year study evaluated 87 San Antonio de los Cobres (SAC) Indigenous and 36 Buenos Aires (BA) urban schoolchildren aged 9.7 + 2.1 years between October 2013 and October 2014. SAC children included 70 (80.5%) treated with 100,000 IU/year of vitamin D and 17 (19.5%) untreated; and BA children included 25 (69,5%) treated and 11(30.5%) untreated. BMI, lipids, and 25-hydroxyvitamin D (25(OH)D) concentrations were measured at baseline and after one year. Results: There was a significantly lower prevalence of overweight/obesity in SAC (n = 7; 8%) versus BA (n = 7; 36.4%) children. There was a significant association between changes in (25(OH)D) and changes in HDL-C levels in SAC (r0.44;p < 0.01) and in BA (r0.34;p < 0.05). Multiple linear regression analyses showed that changes in (25(OH)D ) were significantly associated with changes in HDL-C in SAC (Beta = 0.55, p = 0.02; R20.11) and BA children (Beta = 0.42, p = 0.04; R2 0.21) adjusted for age, gender, and BMI. Furthermore, multiple logistic regression analysis showed that children in the treated group had a likelihood six times greater of having HDL-C >40 mg/dL than the untreated group, adjusted for age, gender, and BMI (OR 6.3: CI 2.0 - 19.8; p < 0.01). Conclusion: These results suggest that children who had received vitamin D supplementation had significantly higher vitamin D status and HDL-C, as compared with non-supplemented children in both communities.
... However, not all studies have reported reductions in skeletal muscle cross-sectional area with highaltitude exposure (18,26,38,45). It is likely that the discrepancies in muscle cross-sectional area responses to high altitude are because of differences in hypoxic exposure (17), diet, activity, sleep, and water metabolism across studies (30,41). It is also possible that the overall hypoxic dose, which takes into account both the elevation of exposure and the duration of exposure in hours (kmIh j1 = (m/1000) Â h), was insufficient in some studies (18,26,38) to elicit measurable changes in crosssectional area (17). ...
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Effects of environmental hypoxia on fat-free mass are well studied. Negative energy balance, increased nitrogen excretion and fat-free mass loss are commonly observed in lowlanders sojourning at high altitude. Reductions in fat-free mass can be minimized if energy consumption matches energy expenditure. However, in non-research settings, achieving energy balance during high altitude sojourns is unlikely and myofibrillar protein mass is usually lost, but the mechanisms accounting for the loss of muscle mass are not clear. At sea level, negative energy balance reduces basal and blunts postprandial muscle protein synthesis, with no relevant change in muscle protein breakdown. Downregulations in muscle protein synthesis and loss of fat-free mass during energy deficit at sea level are largely overcome by consuming at least twice the recommended dietary allowance for protein. Hypoxia may increase or not affect resting muscle protein synthesis, blunt post-exercise muscle protein synthesis, and markedly increase proteolysis independent of energy status. Hypoxia-induced mTORC1 dysregulation and an upregulation in calpains- and ubiquitin proteasome-mediated proteolysis may drive catabolism in lowlanders sojourning at high altitude. However, the combined effects of energy deficit, exercise and dietary protein manipulations on the regulation of muscle protein turnover have never been studied at high altitude. This article reviews the available literature related to the effects of high altitude on fat-free mass, highlighting contemporary studies that assessed the influence of altitude exposure (or hypoxia) on muscle protein turnover and intramuscular regulation of muscle mass. Knowledge gaps are addressed and studies to identify effective and feasible countermeasures to hypoxia-induced muscle loss are discussed.
... Humans living at high altitudes are both less likely to have obesity and to be diagnosed with new onset obesity (8). Chronic hypoxia, increased plasma leptin concentrations, and impaired intestinal function are among the hypotheses given to explain altitude-induced weight loss (9). At high altitude, hypoxic induction of Epo regulated in part by hypoxia inducible factor-2 and prolyl hydroxylase domain-containing protein 2 offers a potential alternative explanation (10). ...
Article
Objective: To investigate the concurrent relationships between human plasma erythropoietin concentrations and energy expenditure (EE), body composition, plasma leptin concentrations, and associations with weight change. Methods: Plasma to measure erythropoietin and leptin; data for body composition; 24-h EE measured in a whole-room calorimeter; and 75 g oral glucose tolerance testing were available from 109 full-heritage Pima Indians (55% male) from a larger study designed to understand the causes of obesity. Seventy-nine subjects had data for weight at a later visit (mean follow-up = 4.3 ± 1.9 years) to calculate percent weight change per year. Results: Erythropoietin, adjusted for covariates, correlated with 24-h EE (r = 0.26, P = 0.007), sleeping EE (r = 0.29, P = 0.003), fat-free mass (r = 0.19, P = 0.05), and fat mass (r = 0.27, P = 0.005), but not insulin or glucose measures. The association of erythropoietin with 24-h EE was fully mediated by fat-free mass. Erythropoietin associated with leptin in women (ρ = 0.36, P = 0.01), but not in men (P = 0.9), independently from fat mass. The association of erythropoietin with percent weight change per year was in opposing directions (interaction: P = 0.002) in males (r = -0.35, P = 0.02) versus females (r = 0.37, P = 0.02). Conclusions: Non-hematopoietic endogenous erythropoietin action may be involved in body weight regulation in opposing directions in men and women, i.e., weight loss in men and weight gain in women.
... La diminution de l'apport énergétique observée en haute altitude est donc un déterminant majeur de la perte de poids. Plusieurs causes peuvent être reliées à ce phénomène, la principale serait l'anorexie occasionnée simplement par la haute altitude ou par le mal des montagnes (Acute mountain sickness) [3,16,17,20] . L'apport calorique quotidien des randonneurs lors d'un trek aurait tendance à se situer bien en deçà des recommandations. ...
... Hypoxia inducible factor 1 has been linked to plasma leptin -a hormone secreted by adipose tissue that produces negative feedback on appetiteand inversely associated with obesity [30]. This could be a plausible explanation for the inverse association between obesity prevalence and elevation [31]. ...
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Background: Epidemiological studies have suggested an inverse association between circulating levels of vitamin D and cardiovascular disease risk biomarkers, including an atherogenic lipid profile. Objective: To compare the prevalence and the distribution of lipid levels among vitamin D supplemented Argentinean indigenous San Antonio de los Cobres (SAC) children with a nonsupplemented Buenos Aires (BA) mixed population group. Methods: A group of indigenous children from SAC with hypovitaminosis D supplemented with vitamin D; and a nonsupplemented group from a BA mixed population were compared via a cross sectional study. Anthropometric measures, glucose, lipids, vitamin D, and insulin were measured. Results: The mean ages were 10.3 + 2.3 in SAC and 8.7 ± 1.8 years in BA children. There was a lower prevalence of overweight 7.9%(15/192) vs 17.8% (23/129); and of obesity 1.6% (3/192) vs 30.2% (39/129) in SAC vs. BA respectively. Approximately half of the SAC children versus 30% from BA had optimal vitamin D levels (≥30ng/mL). There was a significantly higher prevalence of high triglycerides (TG) (27.6%vs 4.6%) and low HDL-C (21.3% vs 5.4%) in SAC vs BA children, respectively. In separate linear regression models, we found that despite effective vitamin D repletion, SAC children had higher TG and TG/HDL-C values, whereas HDL-C levels were lower than those of BA children adjusted for age, gender, BMI, and insulin levels. Conclusion: Indigenous Argentinean children have a higher risk for dyslipidemia in comparison with BA children, even after vitamin D treatment, suggesting that dyslipidemia could be related to diet or ethnic backgrounds.
... Convergent patterns have also been observed in multiple of species at high altitudes, which were consistent with the hypoxia treatment conducted in previous laboratory experiments ( Suzuki et al., 2018). Moreover, weight loss was common in animals based on long sojourn times at high altitudes ( Hamad and Travis, 2006; Westerterp and Kayser, 2006). The overall alpha-diversity and beta-diversity measurements, based on the rarefied OTUs in this study, were higher in the low-altitude groups than in the high-altitude groups, and a higher diversity is generally considered to be a mark of a healthy and resilient microbiota (Petersen and Round, 2014). ...
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The gut microbiota is a complex and essential system organ that plays an integrative role in balancing key vital functions in the host. Knowledge of the impact of altitude on the gut microbiota of European mouflon (Ovis orientalis musimon) and blue sheep (Pseudois nayaur) is currently limited. In this study, we compared the characteristics of gut microbiota in 5 mouflon at low altitude (K group), 4 mouflon at high altitude (L group), 4 blue sheep at low altitude (M group), and 4 blue sheep at high altitude (N group). The V3–V4 region of the 16S rRNA gene was analyzed using high-throughput sequencing. Analyses based on the operational taxonomic units showed significant changes in the gut microbial communities between groups at different altitudes. At the phylum level, groups at the high altitudes had a higher relative abundance of Firmicutes and a lower relative abundance of Bacteroidetes than those at the low altitudes. A higher Firmicutes:Bacteroidetes ratio is beneficial to animals in terms of the gut microbiota-mediated energy harvest. The relative abundance of Proteobacteria was significantly higher in the gut microbiota of mouflon sheep at high altitudes. At the genus level, the Bacteroides:Prevotella ratio was significantly higher in the low-altitude group (than the high-altitude group) of mouflon sheep and the ratio was significantly higher in the high-altitude group (than the low-altitude group) in blue sheep. In addition, the Ruminococcaceae_UCG-005 related to cellulose and starch digestion was the predominant genus in blue sheep and the relative abundance of the genus was significant higher in the high-altitude group than the low-altitude group of blue sheep (P < 0.01). In conclusion, our results suggested that the gut microbiota of high-altitude groups of sheep had stronger abilities related to energy metabolism and the decomposition of substances, e.g., fiber and cellulose, and that such abilities are associated with high-altitude adaptation.
... 스프린트성 운동(경사도 10%, 스피드 17 km/hr) 전ㆍ 후 및 회복 5, 10, 60분에 카테터(Kovax-cath, Korea)를 이용, 전완정중정맥에서 7 ml를 채혈해 CPK와 LDH를 분광광도계(Biomedical Science, USA)로 분석하였다 (Kyara & Kenneth, 1999 (Yingzhong et al., 2006;Lippl et al., 2010), 단백질 분해효소의 증가 (Cymerman, 1996) 등으로 체지방량과 근육량을 감소시킨 다 (Hamad & Travis, 2006;Netzer et al., 2008;Wiesner et al., 2009 (Melissa et al., 1997;Yu et al., 1999 (Mizuno et al., 1990;Moton & Cable, 2005 (Bahr & Sejersted, 1992). 따라서 남자의 경우에 자전거 운동의 적정강도는 체중에 일정한 상수(0.075)를 ...
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Ham, J. H., Nam, S. S., Park, H. Y., Sunoo, S. Effects of 4 weeks intermittent sprint training on anaerobic energy metabolites and performance in hypobaric hypoxic condition, equivalent to an altitude of 3,000 m. Exercise Science. 20(4): 461-474, 2011. The study was designed to investigate the effects of intermittent sprint training in hypobaric hypoxic condition, equivalent to an altitude of 3,000 m and sea level on anaerobic energy metabolism and performance. Fourteen college male students majoring sports volunteered to participate in this research. Running grade, speed, time, repetition time, and interval between running were 10 percent, 15-17 km/hr, 30 seconds, 10 times, 2 minutes respectively. Training period was 4 weeks. They took 8 weeks rest after first training (4 weeks) in 3,000 m simulated altitude and sea level. Also second training practiced 4 weeks in that order (a cross-over study). The results of this study were as follows. Weight and muscle mass were significantly decreased after 3,000 m simulated altitude training. CPK was not significantly changed after 3,000 m simulated altitude and sea level training. LDH was significantly decreased immediately after exercise and recovery 5 minutes after 3,000 m simulated altitude training. Oxygen transporting capacity of the blood was not significantly changed after 3,000m simulated altitude and sea level training. EPOC was significantly increased after 3,000 m simulated altitude and sea level training. Anaerobic power was significantly increased after 3,000 m simulated altitude training. Leg isokinetic muscular strength was significantly increased after sea level training. But it was significantly decreased after 3,000 m simulated altitude training. 100 m time trial was significantly decreased after 3,000 m simulated altitude training. But 400 m time trial was not significantly changed in two groups. We have demonstrated that weight, muscle mass and 100 m time trial was significantly changed by 4 weeks of intermittent sprint training in hypobaric hypoxic condition, equivalent to an altitude of 3,000 m, whereas the other physiological parameters was not significantly changed in two groups. 초 록 함주호, 남상석, 박훈영, 선우 섭. 3,000 m 상당고도 저압·저산소 환경에서 4주간의 간헐적인 스프린트 훈련이 무산소성 에너지대사와 운동수행능력에 미치는 영향. 운동과학, 제20권 4호 461-474, 2011. 본 연구는 3,000 m 상당고도와 평지에서 간헐적인 스프린트 훈련이 무산소성 에너지대사와 운동수행능력에 미치는 영향을 cross-over study로 비교한 것이다. 연구의 대상자들은 체육전공 남자 대학생 14 명으로, 트레드밀 달리기를 경사도 10%, 스피드 15∼17 km/hr의 운동 강도로 4주간, 주 3회, 30초×10세트, 세트 간 휴식은 2분으로 하 였으며, 3,000 m 상당고도(526 mmHg)와 평지(760 mmHg)에서, 각각 1차 트레이닝을 실시한 후 8주간의 휴식기를 거친 후 2차 트레이닝 을 실시하였다. 그 결과 체중과 근육량은 3,000 m 상당고도 트레이닝 후에 유의하게 감소하였다. CPK는 두 조건 모두 트레이닝 후에 유의한 변화가 없었으나, LDH는 3,000 m 상당고도 트레이닝 후에 고강도 운동직후와 회복 5분에 유의하게 감소하였다. 혈중산소운반능 력은 두 조건 모두 트레이닝 후에 유의한 변화가 없었다. EPOC는 평지 및 3,000 m 상당고도 트레이닝 후에 유의하게 증가하였다. 무산 소성 파워는 3,000 m 상당고도 트레이닝 후에 유의하게 증가 하였다. 하지근 등속성 근력은 평지 트레이닝 후에 유의하게 증가 하였으 나, 3,000 m 상당고도 트레이닝 후에는 유의하게 감소하였다. 100 m time trial은 3,000 m 상당고도 트레이닝 후에 유의하게 감소하였으 나, 400 m time trial은 두 조건 모두 유의한 변화가 없었다. 주요어 : 3,000 m 상당 저압・저산소, Cross-over suty, 해당과정 효소, 산소운반능력, EPOC, 무산소성 파워, 퍼포먼스 운동과학, 2011년, 제20권 제4호
... Participants started consuming controlled diets on day 1, the first full day of residence at 4,300 m, and continued until the end of the sojourn at HA (phase 2). Diets contained either a standard amount of protein (1.1 g/kg/day; n = 8) or higher amount of protein (2.1 g/kg/day; n = 9), and were designed to induce weight loss, which is common during military training and operations, and during HA sojourn (Hamad and Travis, 2006). ...
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Human Molecular and Physiological Responses to Hypoxia Towards the end of the 19th century, the French physician Denis Jourdan was the first to understand and state the critical role of the reduction of oxygen at altitude, which he defined as anoxemia. This term indicated the diminished quantity of oxygen contained in the blood of people living at high altitude, where the tension of the oxygen in the surrounding air is considerably decreased (West and Richalet, 2013). In the following 150 years, studies on hypoxia took off, ranging from purely clinical and functional aspects to cellular and biomolecular ones, from acute to chronic hypoxia and analyzing not only the altitude-hypoxia but also the hypoxia related to underlying diseases. Currently, the study of pathophysiological responses at altitude is a model to investigate the mechanisms of response to hypoxia in any condition, also in critical illnesses (Grocott et al., 2007). In this special issue, a series of ten articles with different approaches applied to the study of molecular and physiological responses to hypoxia were collected.
... In this context, it has been described that pre-adipocytes express RANKL in the adipose tissue of bone marrow. That directly contributes to the osteoclastic activity and bone resorption, which is associated to aging [84,87] . Our results showed that CH exposure can reverse the induction of RANKL expression, in the early stages of adipogenesis, while inducing OPG expression, in MSC induced to differentiate into adipocytes. ...
Article
BACKGROUND Mesenchymal stem cells (MSC) of bone marrow are the progenitor of osteoblasts and adipocytes. MSC tend to differentiate into adipocytes, instead of osteoblasts, with aging. This favors the loss of bone mass and development of osteoporosis. Hypoxia induces hypoxia inducible factor 1α gene encoding transcription factor, which regulates the expression of genes related to energy metabolism and angiogenesis. That allows a better adaptation to low O2 conditions. Sustained hypoxia has negative effects on bone metabolism, favoring bone resorption. Yet, surprisingly, cyclic hypoxia (CH), short times of hypoxia followed by long times in normoxia, can modulate MSC differentiation and improve bone health in aging. AIM To evaluate the CH effect on MSC differentiation, and whether it improves bone mineral density in elderly. METHODS MSC cultures were induced to differentiate into osteoblasts or adipocytes, in CH (3% O2 for 1, 2 or 4 h, 4 d a week). Extracellular-matrix mineralization and lipid droplet formation were studied in MSC induced to differentiate into osteoblast or adipocytes, respectively. In addition, gene expression of marker genes, for osteogenesis or adipogenesis, have been quantified by quantitative real time polymerase chain reaction. The in vivo studies with elderly (> 75 years old; n = 10) were carried out in a hypoxia chamber, simulating an altitude of 2500 m above sea level, or in normoxia, for 18 wk (36 CH sessions of 16 min each). Percentages of fat mass and bone mineral density from whole body, trunk and right proximal femur (femoral, femoral neck and trochanter) were assessed, using dual-energy X-ray absorptiometry. RESULTS CH (4 h of hypoxic exposure) inhibited extracellular matrix mineralization and lipid-droplet formation in MSC induced to differentiate into osteoblasts or adipocytes, respectively. However, both parameters were not significantly affected by the other shorter hypoxia times assessed. The longest periods of hypoxia downregulated the expression of genes related to extracellular matrix formation, in MSC induced to differentiate into osteoblasts. Interestingly, osteocalcin (associated to energy metabolism) was upregulated. Vascular endothelial growth factor an expression and low-density lipoprotein receptor related protein 5/6/dickkopf Wnt signaling pathway inhibitor 1 (associated to Wnt/β-catenin pathway activation) increased in osteoblasts. Yet, they decreased in adipocytes after CH treatments, mainly with the longest hypoxia times. However, the same CH treatments increased the osteoprotegerin/receptor activator for nuclear factor kappa B ligand ratio in both cell types. An increase in total bone mineral density was observed in elderly people exposed to CH, but not in specific regions. The percentage of fat did not vary between groups. CONCLUSION CH may have positive effects on bone health in the elderly, due to its possible inhibitory effect on bone resorption, by increasing the osteoprotegerin / receptor activator for nuclear factor kappa B ligand ratio.
... In addition to this, previous research has stated that changes in body composition during the elderly require long-term physical exercise programs maintained over time [33,34]. Changes in body composition are the result of several single contributors related to diet, physical exercise performed, and type/dose of hypoxia received [35]. In relation to diet and the lack of improvement observed in BMC and BMD levels, it is also important to highlight that the intake of calcium and vitamin D (boosters of bone formation) of our participants were below RDI. ...
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Aging is associated with metabolic alterations, and with a loss of strength, muscle and bone mass. Moderate intermittent hypoxia has been proposed as a new tool to enhance health-related function. The aim of this study was to evaluate the effect of moderate intermittent hypoxia exposures on parameters related to cardiovascular and bone health in older adults. A total of 38 healthy older adults (aged 65–75 years) were divided into two groups: control group (C), and hypoxia group (H) that was subjected to an intermittent hypoxia exposure (at simulated altitude of 2500 m asl) during a 24-week period (3 days/week). Body composition, blood pressure, metabolic parameters (Cholesterol, triglycerides and glucose), C-reactive protein (CRP), vascular cell adhesion molecule-1 (VCAM-1), interleukin 8 (IL-8), interleukin 10 (IL-10), N-terminal propeptide of type I procollagen (PINP) and beta C-terminal telopeptide of collagen bone formation (b-CTX) were analyzed before and after the intervention. A repeated measures analysis of variance was performed to evaluate between-group differences. The results showed that the hypoxia group achieved after the intervention a decrease in fat mass, CRP (pro-inflammatory biomarker) and b-CTX (bone resorption biomarker), as well as an increase in PINP (bone formation biomarker). In conclusion, the intermittent hypoxia might be a useful therapeutic tool to deal with problems associated with aging, such as the increase in body fat, the loss of bone mass or low-grade inflammation.
... Hypoxia-induced oxidative stress might contribute to the formation of GI lesions such as peptic ulcers (10), and hypoxic stress in the GI tract can damage intestinal microvasculature leading to high-altitude GI bleeding (6). A damaged intestinal barrier may impair nutrient absorption which could explain some of the weight loss observed during prolonged exposures to high altitude (11)(12)(13)(14). In addition, intestinal barrier injury can allow for luminal contents to pass through the intestinal wall, a process known as increased intestinal permeability. ...
Article
Gastrointestinal complaints are often reported during ascents to high altitude (> 2500 m), though their etiology is not known. One potential explanation is injury to the intestinal barrier which has been implicated in the pathophysiology of several diseases. High altitude exposures can reduce splanchnic perfusion and blood oxygen levels causing hypoxic and oxidative stress. These stressors might injure the intestinal barrier leading to consequences such as bacterial translocation and local/systemic inflammatory responses. The purpose of this mini review is to 1) discuss the impact of high-altitude exposures on intestinal barrier dysfunction, and 2) present medications and dietary supplements which may have relevant impacts on the intestinal barrier during high-altitude exposures. There is a small but growing body of evidence which shows that acute exposures to high altitudes can damage the intestinal barrier. Initial data also suggests that prolonged hypoxic exposures can compromise the intestinal barrier through alterations in immunological function, microbiota, or mucosal layers. Exertion may worsen high-altitude related intestinal injury via additional reductions in splanchnic circulation and greater hypoxemia. Collectively these responses can result in increased intestinal permeability and bacterial translocation causing local and systemic inflammation. More research is needed to determine the impact of various medications and dietary supplements on the intestinal barrier during high-altitude exposures.
... That is, hypoxia helps to transform slow twitch fibers (Type I) into fast twitch fibers (Type II) (28). In addition, the enhanced capability to transport oxygen in the blood relates to an increase in the burning rate of calories and the delivery of oxygen to different muscles that contribute to a more effective fat oxidation process and a reduction in body fat (8,30,37). ...
Article
Namboonlue C, Yuyongsin S, Wanna S, Muangritdech N. The Effects of Five Weeks Low-Intensity Aerobic Training Under Hypoxia on Body Composition and Oxygen Consumption in Overweight/Obesity Men. JEPonline 2021;24(4):33-44. The purpose of this study was to examine and compare the effects of low-intensity aerobic training under moderate hypoxia on body composition, muscle strength-endurance and maximum oxygen uptake of overweight or obese males. Twenty healthy overweight or obese males, aged 19 to 24 years, from Ubon Ratchathani Rajabhat University were randomly divided into 2 Groups: (a) Control Group (Normoxia; NORM, FIO2 = 20.9%); and the (b) Experimental Group (Hypoxia; HYP, FIO2 = 15.8%). Both Groups performed low-intensity aerobic training for 30 min^d⁻¹, 3 d^wk⁻¹ over a 5-week period at 60% heart rate reserve, while the subjects in the NORM performed exercise under normoxic condition. All variables were measured before and after the 5weeks of the experimental period. The number of repetitions in the knee flexion and maximum oxygen uptake were significantly increase in the HYP (31.0 ± 18.4% and 18.9 ± 14.7%, mean ± SD) compared with the NORM (17.5 ± 13.0% and 6.8 ± 4.7) Similarly, HYP showed a substantial decrease in body weight, body mass index, body fat, and visceral adipose tissue (-2.3 ± 2.8%, -2.6 ± 3.0%, -7.9 ± 10.5%, and -12.0 ± 15.0%, respectively) when compared to their baseline with no significant difference between the 2 Groups. Low-intensity aerobic training under hypoxia could be used as an alternative and novel therapeutic strategy to improve body composition and oxygen consumption in overweight or obese subjects.
... Participants started consuming controlled diets on day 1, the first full day of residence at 4,300 m, and continued until the end of the sojourn at HA (phase 2). Diets contained either a standard amount of protein (1.1 g/kg/day; n = 8) or higher amount of protein (2.1 g/kg/day; n = 9), and were designed to induce weight loss, which is common during military training and operations, and during HA sojourn (Hamad and Travis, 2006). ...
Article
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Individuals sojourning at high altitude (≥2,500m) often develop acute mountain sickness (AMS). However, substantial unexplained inter-individual variability in AMS severity exists. Untargeted metabolomics assays are increasingly used to identify novel biomarkers of susceptibility to illness, and to elucidate biological pathways linking environmental exposures to health outcomes. This study used untargeted nuclear magnetic resonance (NMR)-based metabolomics to identify urine metabolites associated with AMS severity during high altitude sojourn. Following a 21-day stay at sea level (SL; 55m), 17 healthy males were transported to high altitude (HA; 4,300m) for a 22-day sojourn. AMS symptoms measured twice daily during the first 5days at HA were used to dichotomize participants according to AMS severity: moderate/severe AMS (AMS; n =11) or no/mild AMS (NoAMS; n =6). Urine samples collected on SL day 12 and HA days 1 and 18 were analyzed using proton NMR tools and the data were subjected to multivariate analyses. The SL urinary metabolite profiles were significantly different ( p ≤0.05) between AMS vs. NoAMS individuals prior to high altitude exposure. Differentially expressed metabolites included elevated levels of creatine and acetylcarnitine, and decreased levels of hypoxanthine and taurine in the AMS vs. NoAMS group. In addition, the levels of two amino acid derivatives (4-hydroxyphenylpyruvate and N-methylhistidine) and two unidentified metabolites (doublet peaks at 3.33ppm and a singlet at 8.20ppm) were significantly different between groups at SL. By HA day 18, the differences in urinary metabolites between AMS and NoAMS participants had largely resolved. Pathway analysis of these differentially expressed metabolites indicated that they directly or indirectly play a role in energy metabolism. These observations suggest that alterations in energy metabolism before high altitude exposure may contribute to AMS susceptibility at altitude. If validated in larger cohorts, these markers could inform development of a non-invasive assay to screen individuals for AMS susceptibility prior to high altitude sojourn.
... That is, hypoxia helps to transform slow twitch fibers (Type I) into fast twitch fibers (Type II) (28). In addition, the enhanced capability to transport oxygen in the blood relates to an increase in the burning rate of calories and the delivery of oxygen to different muscles that contribute to a more effective fat oxidation process and a reduction in body fat (8,30,37). ...
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Namboonlue C, Yuyongsin S, Wanna S, Muangritdech N. The Effects of Five Weeks Low-Intensity Aerobic Training Under Hypoxia on Body Composition and Oxygen Consumption in Overweight/Obesity Men. JEPonline 2021;24(4):33-44. The purpose of this study was to examine and compare the effects of low-intensity aerobic training under moderate hypoxia on body composition, muscle strength-endurance and maximum oxygen uptake of overweight or obese males. Twenty healthy overweight or obese males, aged 19 to 24 years, from Ubon Ratchathani Rajabhat University were randomly divided into 2 Groups: (a) Control Group (Normoxia; NORM, FIO2 = 20.9%); and the (b) Experimental Group (Hypoxia; HYP, FIO2 = 15.8%). Both Groups performed low-intensity aerobic training for 30 min·d-1 , 3 d·wk-1 over a 5-week period at 60% heart rate reserve, while the subjects in the NORM performed exercise under normoxic condition. All variables were measured before and after the 5-weeks of the experimental period. The number of repetitions in the knee flexion and maximum oxygen uptake were significantly increase in the HYP (31.0 ± 18.4% and 18.9 ± 14.7%, mean ± SD) compared with the NORM (17.5 ± 13.0% and 6.8 ± 4.7) Similarly, HYP showed a substantial decrease in body weight, body mass index, body fat, and visceral adipose tissue (-2.3 ± 2.8%,-2.6 ± 3.0%,-7.9 ± 10.5%, and-12.0 ± 15.0%, respectively) when compared to their baseline with no significant difference between the 2 Groups. Low-intensity aerobic training under hypoxia could be used as an alternative and novel therapeutic strategy to improve body composition and oxygen consumption in overweight or obese subjects.
... [154] ont montré chez des sujets sains qu'une exposition continue à l'altitude simulée (4300 m) durant une semaine améliore la tolérance des cellules au glucose. Par ailleurs, il a été montré que l'exposition durant quelques jours voire quelques semaines à l'hypoxie hypobarique améliore le métabolisme basal dès les premiers jours d'ascension en montagne [155][156][157]. Cette augmentation dépend de l'altitude à laquelle les sujets sont exposés : +6% à 3650 m, +10% et +27% à 3800 m et 4300 m, respectivement [155,158,159]. ...
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L’hypoxie désigne une baisse de la biodisponibilité en oxygène au niveau tissulaire. La combinaison de l’hypoxie intermittente et de l’hypercapnie est identifiée dans le cadre de plusieurs maladies respiratoires comme un élément physiopathologique déterminant. Cependant, des travaux de recherche suggèrent qu’une exposition à l’hypoxie hypo- ou normocapnique à l’éveil peut améliorer la santé cardiovasculaire. La combinaison d’une exposition hypoxique et de l’entraînement à l’effort est utilisée par les athlètes pour améliorer la performance sportive aérobie. Des études pilotes récentes y compris chez le malade chronique indiquent que l’exposition à l’hypoxie modérée au repos ou à l’effort chez le patient est susceptible d’induire des gains significatifs en termes de santé cardiovasculaire, de composition corporelle et de statut métabolique.Nous nous sommes intéressés aux effets cardiorespiratoires et tissulaires de l’exposition hypoxique normobarique chez le sujet sain et chez la personne en surpoids ou obèse présentant un risque ou des anomalies cardio-métaboliques. Nous avons étudié l’efficacité de 2 types de conditionnement au repos consistant en une hypoxie continue ou une hypoxie intermittente et un entraînement à l’effort hypoxique par comparaison à la situation normoxique. Nous avons tout d’abord étudié les effets d’une exposition hypoxique à court terme au repos chez 14 sujets sains. Nous avons ensuite étudié les effets cardiorespiratoires, tissulaires, vasculaires et métaboliques d’un programme de conditionnement hypoxique normobarique à moyen terme au repos chez 35 patients en surpoids ou obèse. Nous avons de plus réalisé chez 24 sujets sains une étude préliminaire afin de vérifier la faisabilité et de caractériser les réponses cardio-respiratoires et l’oxygénation tissulaire au cours d’un exercice aigu à charge constante d’intensité modérée ou intermittent intense en hypoxie comparé à une condition placébo normoxique. La dernière étude a consisté à étudier les conséquences cardiorespiratoires, tissulaires, vasculaires et métaboliques d’un programme d’entraînement à l’effort en hypoxie par rapport au même programme en normoxie chez 23 patients en surpoids ou obèses.L’étude réalisée chez le sujet sain met en évidence l’intérêt à court terme d’un conditionnement hypoxique intermittent au repos sur des variables associées aux risques cardiovasculaires (diminution de la pression artérielle systolique en normoxie et augmentation de la variabilité sinusale) et une modulation de l’hypoxie tissulaire. Nous avons montré chez le sujet sain que l’hypoxie combiné à l’exercice aigu provoque une diminution de l’oxygénation musculaire similaire mais une diminution de l’oxygénation du cortex préfrontal plus importante par comparaison à un effort normoxique à même intensité relative. Ensuite, chez le sujet en surpoids ou obèse, nous avons montré que le conditionnement hypoxique passif chronique induit une diminution de la pression artérielle diastolique de repos en normoxie, une augmentation de la réponse ventilatoire hypoxique et une diminution de la variabilité cardiaque (après conditionnement par hypoxie intermittente seulement) et que le conditionnement hypoxique actif chronique améliore l’aptitude maximale aérobie par rapport à une situation placébo normoxique.Les résultats obtenus montrent la faisabilité de plusieurs conditionnements hypoxiques prometteurs au plan vasculaire y compris chez le sujet en surpoids ou obèse limité à l’exercice musculaire. Le conditionnement hypoxique actif montre également des bénéfices accrus sur l’aptitude aérobie. Ces protocoles de conditionnement doivent être affinés en vue d’optimiser leur efficacité en termes de perte de poids et d’amélioration du risque cardio-vasculaire et métabolique dans des populations présentant une obésité associée à une morbidité cardio-métabolique. Ils représentent également une piste thérapeutique innovante dans d’autres pathologies chroniques
... report a suppressive effect of endocrine mediators to facilitate maximal energy efficiency even at the cost of better oxygen delivery [4,5]. Weight loss is a highly studied phenomenon during chronic low pO 2 exposure and is attributed in part to hormones like leptin [6][7][8][9][10][11]. Physiological features like heartbeat interval distributions were reported to be affected by chronic hypobaric hypoxia [12]. ...
Article
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Extended exposure to low pO2 has multiple effects on signaling cascades. Despite multiple exploratory studies, omics studies elucidating the signaling cascades essential for surviving extended low pO2 exposures are lacking. In this study, we simulated low pO2 (PB = 40 kPa; 7620 m) exposure in male Sprague–Dawley rats for 3, 7 and 14 days. Redox stress assays and proteomics based network biology were performed using lungs and plasma. We observed that redox homeostasis was achieved after day 3 of exposure. We investigated the causative events for this. Proteo-bioinformatics analysis revealed STAT3 to be upstream of lung cytoskeletal processes and systemic lipid metabolism (RXR) derived inflammatory processes, which were the key events. Thus, during prolonged low pO2 exposure, particularly those involving slowly decreasing pressures, redox homeostasis is achieved but energy metabolism is perturbed and this leads to an immune/inflammatory signaling impetus after third day of exposure. We found that an interplay of lung cytoskeletal elements, systemic energy metabolism and inflammatory proteins aid in achieving redox homeostasis and surviving extended low pO2 exposures. Qualitative perturbations to cytoskeletal stability and innate immunity/inflammation were also observed during extended low pO2 exposure in humans exposed to 14,000 ft for 7, 14 and 21 days.
... Most prior work assessing changes to body composition in similar but non-NOLS settings (i.e., mountaineering, backpacking, etc.) are limited to shorter-term expeditions, that last a couple weeks (Hamad & Travis, 2006;Zaccagni et al., 2014). However, across the course of~3 months, if a population has acclimatized to their surrounding environment and has ample nutrition, they would likely return to their starting body mass and potentially exhibit readjusted body fat and lean muscle, as we see here. ...
Article
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Objectives An energetically demanding environment like a wilderness expedition can lead to potent stressors on human physiology and homeostatic balance causing shifts in energy expenditure and body composition. These shifts likely have consequences on overall health and performance and may potentially differ by sex. It is therefore critical to understand the potential differential body composition and energy expenditure changes in response to a novel and challenging environment in both males and female bodies. Methods Data were collected from 75 healthy individuals (female = 41; ages 18–53) throughout a 3-month long expedition in the American Rockies. Body mass, body fat, and lean muscle mass were measured before, during, and after the course. Physical activity intensity and energy expenditure were also measured in a subset of participants using the wGT3X-BT Actigraph wrist monitor and an accompanying Bluetooth heart rate monitor. Results Over the 3-month period, individuals initially experienced declines in body mass, body fat percentage, and lean muscle mass. Participants partially rebounded from these deficits to maintain overall body mass with a slight recomposition of body fat and lean muscle mass. Our data also demonstrated that sex moderated total energy expenditure, where females experienced a modest decline whereas males experienced an increase in energy expenditure from the beginning to the end of the course. Conclusions Understanding changes in energy storage in the body and variation in energy expenditure between sexes during a 3-month expedition has critical implications for maintaining health and performance in an energetically demanding environment where resources may be scarce.
... Alternatively, hypoxic training enhances the aerobic performance and reduces the obesity and obesity-related diseases by improving aerobic metabolic process (e.g., enhanced oxygen transportation and utilization capacity) [5,13,[25][26][27]. Generally, exercise under moderate hypoxia is an effective method for weight loss and improving body composition through various physiological responses and adaptations such as an increase in activity of appetite-related gut hormones and adipocytokines, a change in energy substrate utilization, an increase in the energy metabolic rate, a reduction in perception of hunger feeling and in food intake, and an increase in the activity of various endocrine factors [1,27,28]. Additionally, hypoxic training increases the secretion of insulin, insulin-like growth factor-1, erythropoietin, and sex hormones such as androgens and testosterone, which increase the muscle mass and basal metabolic rate [5,[29][30][31]. Based on these rationales, previous studies have verified the effectiveness of a 4-12-week aerobic exercise under moderate hypoxia (F i O 2 : 16.5-14.5%, ...
Article
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This study examined the effect of Pilates training under hypoxia, a novel treatment method, for obesity. Thirty-two Korean women with obesity (age: 34-60 (47.5 ± 7.5) years) were randomly assigned to control (CON; n = 10), normoxic Pilates training (NPTG; n = 10), and hypoxic Pilates training groups (HPTG; n = 12). The NPTG and HPTG performed 50 min of Pilates training using a tubing band for 12 weeks (3 days/week) in their respective environmental conditions (NPTG: normoxic condition, inspired oxygen fraction (FiO2) = 20.9%; HPTG: moderate hypoxic condition, FiO2 = 14.5%). The CON maintained their daily lifestyle without intervention. All subjects underwent body composition, blood pressure, arterial stiffness, vascular endothelial function, cardiometabolic biomarker, hemorheological function, and aerobic performance measurements before and after the intervention. The HPTG showed a significant improvement in diastolic blood pressure, total cholesterol and triglyceride concentrations, flow-mediated dilation, and erythrocyte deformability and aggregation (all p < 0.05) compared with the CON and NPTG. However, compared with the CON and NPTG, the HPTG did not show improvement in other parameters. Hypoxic Pilates intervention is a novel and successful method for promoting endothelial and hemorheological functions in women with obesity.
... Hypoxic environments have been shown to influence a person's body composition (e.g., reductions in body weight, fat-free mass, fat mass, muscle mass and/or body water) 14 . Tibetans live on the Qinghai-Xizang Plateau, which is a typical plateau environment. ...
Article
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Sarcopenia is an age-associated disease characterized by loss of muscle mass and function, but the diagnostic cutoff values remain controversial. To investigate the diagnostic cutoff values and incidence of sarcopenia in a plateau population, the limb skeletal muscle mass, gait speed and grip strength of 2318 Tibetan adults were measured according to the criteria of the Asian Working Group for Sarcopenia. We found that the diagnostic reference values for sarcopenia in the high-altitude population were significantly lower than those in the plain population, and the incidences of sarcopenia in the high-altitude population over 60 years old were 17.2% in men and 36.0% in women, which were significantly higher than those in the plain population. Our study proposes reference values for the diagnosis of sarcopenia in Tibet. We suggest that the cutoff value for sarcopenia in the plateau population should be established based on altitude. Hypoxia may be an important risk factor for sarcopenia.
... However, Westerterp and Kayser [77] suggested that carbohydrates are a better energy source than proteins at high altitudes, because of their low thermogenesis values (5-10% for carbohydrates, and 20-30% for proteins), and because they require less oxygen to metabolize, which is an advantage in the low-oxygen environment of high altitudes. A carbohydrate-rich diet increases the respiratory quotient, which thus provides high oxygen saturation in the blood [78]. ...
Article
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The ecological requirements of brown bears are poorly known in the Himalaya region, which complicates conservation efforts. We documented the diet of the Himalayan brown bear (Ursus arctos isabellinus) by combining classical scat analysis and a newly developed molecular genetic technique (the trnL approach), in Deosai National Park, Pakistan. Brown bears consumed over 50 plant species, invertebrates, ungulates, and several rodents. Eight plant families; Poaceae, Polygonaceae, Cyperaceae, Apiaceae, Asteraceae, Caryophyllaceae, Lamiaceae, and Rubiaceae were commonly eaten with graminoids comprising the bulk of the diet. Golden marmots comprised the major mammalian biomass in the park, and were also the main meat source for bears. Animal matter, making 36% of dietary content, contributed half of the digestible energy, due to its higher nutritious value. We did not find a significant temporal pattern in diet, perhaps because the availability of the major diet (graminoids) did not change over the foraging period. Male brown bears were more carnivorous than females, probably because of their larger size, which requires higher energy and also makes them more efficient in capturing marmots. Frequencies of three plant species were also significantly higher in male brown bears; Bistorta affinis, Carex diluta, and Carex sp. Diet of the brown bear differed significantly between the park and surrounding valleys. In valleys, diet consisted predominantly of graminoids and crops, whereas the park provided more nutritious and diverse foodThe estimated digestible energy available to brown bears in Deosai was the lowest documented among brown bear populations, due to the lack of fruits and a relatively lower meat content. The low nutritious diet and high cost of metabolism in a high-altitude environment, probably explains the very low reproductive potential of this population.
... The acute hypoxic setting may per se be deleterious both acutely and in the long term. Catabolic manifestations of weight loss and sarcopenia are frequent in hypoxemic patients with COPD (14), or otherwise healthy subjects exposed to high altitude (6,7,27). Likewise, sustained heavy physical exertion is strongly catabolic. ...
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As a model of extreme conditions, eight healthy women, part of a 40-member Nepal mountain-climbing expedition, were monitored for dynamic endocrine adaptations. Endocrine measurements were made at frequent intervals over a 6-10 hours period at four altitudes: 450 m, 4800 m (Base Camp), 6050 m and again at 4800 m (on descent) after an acclimatization period (4800 mA). Quantified hormones were growth hormone (GH), prolactin (PROL), Cortisol (Cort), Thyroid-stimulating hormone (TSH), and free thyroxine. These hormones are important to the anabolic/catabolic balance of the body, and are vital to growth, homeostasis, hypothalamic inhibition, regulation of stress and metabolism. A key secondary question was the degree to which acclimatization can stabilize hormonal disruption. Based upon statistical false discovery rates, the present analyses unveil marked adaptive changes in the thyroid axis at the level of pulsatile secretion of the pituitary hormone TSH and its downstream product, free thyroxine; strong effects upon the mass of GH, TSH, Cortisol and PROL secretion per burst; and prominent pulsatile frequency disruption and recovery for PROL and cortisol. Since pulsatility changes reflect de facto perturbations in hypothalamo-pituitary control mechanisms, the present data introduce the concept of both frequency and amplitude-dependent adaptive control of brain-pituitary neuroendocrine signals under conditions of extreme altitude exertion and exposure.
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External environmental factors can cause an imbalance in intestinal flora. For people living in the extremes of a plateau climate, lack of oxygen is a primary health challenge that leads to a series of reactions. We wondered how intestinal microorganisms might change in a simulated plateau environment, and what changes might occur in the host organism and intestinal microorganisms in the absence of hypoxia-related factors. In this study, mice carrying a knockout of hypoxia-inducible factor 1β ( Hif-1β ) in myeloid cells and wild-type mice were raised in a composite hypoxic chamber to simulate a plateau environment at 5,000 meters of elevation for 14 days. The mice carrying the myeloid Hif-1β deletion displayed aggravated hypoxic phenotypes, significantly greater weight loss, and significantly higher cardiac index values compared with the wild-type group. The levels of some cytokines increased under the hypoxic environment. Analysis of 16S rRNA sequencing results showed that hypoxia had a significant effect on the gut microbiota in both wild-type and Hif-1β -deficient mice, especially on the first day. The Bacteroidaceae family increased continuously from Day 1 to Day 14 in Hif-1β deletion mice, and they represented an obviously different group of bacteria at Day 14 compared with the wild-type mice. Butyrate-producing bacteria, such as Butyricicoccus, were only found in wild-type mice after 14 days in the hypoxic environment. In conclusion, hypoxia caused heart enlargement, greater weight loss and obvious microbial imbalance in myeloid Hif-1β deficient mice. This study reveals genetic and microecological pathways for research on mechanisms of hypoxia.
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In this research, we evaluated the relationship between obesity rates and altitude using a cross-county study design. We applied a geographically weighted regression (GWR) to examine the spatially varying association between adult obesity rates and altitude after adjusting for four predictor variables including physical activity. A significant negative relationship between altitude and adult obesity rates were found in the GWR model. Our GWR model fitted the data better than OLS regression (R2 = 0.583), as indicated by an improved R2 (average R2 = 0.670; range: 0.26–0.77) and a lower Akaike Information Criteria (AIC) value (14,736.88 vs. 15,386.59 in the OLS model). These approaches, evidencing spatial varying associations, proved very useful to refine interpretations of the statistical output on adult obesity. This study underscored the geographic variation in relationships between adult obesity rates and mean county altitude in the United States. Our study confirmed a varying overall negative relationship between county-level adult obesity rates and mean county altitude after taking other confounding factors into account.
Article
Background Studies have shown wide variation in the prevalence of lactose malabsorption across the world, but no systematic reviews or meta-analyses have recently assessed the prevalence of lactose malabsorption in different geographical areas. We aimed to present an updated systematic review and meta-analysis on the prevalence of lactose malabsorption in adults, by countries and regions, and to assess the variation between different testing methods. Methods Studies reporting on prevalence of lactose malabsorption and lactase persistence were identified by searching MEDLINE and Embase from database inception to Nov 2, 2016. We evaluated studies presenting lactose malabsorption or lactase persistence prevalence data in adults and children aged 10 years or older, including cross-sectional and prospective studies, using genotyping, hydrogen breath tests, lactose tolerance tests, and other testing methods. We excluded studies in children younger than 10 years, studies using self-reported data, and studies including inpatients and outpatients at gastroenterological wards. Studies were screened by two authors (CLS and SKF) and data values were extracted by two authors (CLS and SKF) independently. The primary outcome was the prevalence of lactose malabsorption. This study is registered with PROSPERO, number CRD42017064802. Findings We screened 2665 records, and 306 study populations from 116 full-text articles were included (primary sources); data for 144 additional study populations from 59 articles were obtained from review articles, because full-text primary articles could not be obtained (secondary sources). Of the 450 study populations included, 231 were assessed by genotyping, 83 by hydrogen breath tests, 101 by lactose tolerance tests, and 35 by other methods or methods that were not described sufficiently. The studies included 62 910 participants from 89 countries (covering 84% of the world's population). When standardising for country size, the global prevalence estimate of lactose malabsorption was 68% (95% CI 64–72), ranging from 28% (19–37) in western, southern, and northern Europe to 70% (57–83) in the Middle East. When assessing the global prevalence using genotyping data only, the estimate was 74% (69–80), whereas prevalence was 55% (46–65) using lactose tolerance test data, and 57% (46–67) using hydrogen breath test data. Risk of bias was assessed based on ten indicators; 12 of the articles had a score of ten, indicating low risk of bias, 76 had a score of nine, 26 a score of eight, and two articles a score of seven (indicating higher risk of bias). There was substantial heterogeneity between studies within most of the assessed countries. Interpretation Lactose malabsorption is widespread in most of the world, with wide variation between different regions and an overall frequency of around two-thirds of the world's population. Acknowledging regional patterns of lactose malabsorption is important to guide management of gastrointestinal symptoms. Funding None.
Article
High altitude exposure leads to compromised physical performance with considerable weight loss. The major stressor at high altitude is hypobaric hypoxia which leads to disturbance in redox homeostasis. Oxidative stress is a well-known trigger for many high altitude illnesses and regulates several key signaling pathways under stressful conditions. Altered redox homeostasis is considered the prime culprit of high altitude linked skeletal muscle atrophy. Hypobaric hypoxia disturbs redox homeostasis through increased RONS production and compromised antioxidant system. Increased RONS disturbs the cellular homeostasis via multiple ways such as inflammation generation, altered protein anabolic pathways, redox remodeling of RyR1 that contributed to dysregulated calcium homeostasis, enhanced protein degradation pathways via activation calcium-regulated protein, calpain, and apoptosis. Ultimately, all the cellular signaling pathways aggregately result in skeletal muscle atrophy. Dietary supplementation of phytochemicals could become a safe and effective intervention to ameliorate skeletal muscle atrophy and enhance the physical performance of the personnel who are staying at high altitude regions. The present evidence-based review explores few dietary supplementations which regulate several signaling mechanisms and ameliorate hypobaric hypoxia induced muscle atrophy and enhances physical performance. However, a clinical research trial is required to establish proof-of-concept.
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Four elite rowers completed a 12-day altitude training camp living at 1800 m, and training at 1800 m and 915 m, to assess changes in resting metabolic rate (RMR). RMR and body composition were assessed pre- and postcamp. Downward trends in RMR and body composition were observed postaltitude: absolute RMR (percent change: –5.2%), relative RMR (–4.6%), body mass (–1.2%), and fat mass (–4.1%). These variations are likely related to the hypoxic stimulus and an imbalance between training load and energy intake.
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The neuroendocrine system is deeply involved in the adaptive processes to altitude hypoxia exposure, which require a fine-tuned modulation in the homeostatic steady state of several endocrine and metabolic functions. Physical activity (PA) per se is well-known to induce complex hormonal responses, which greatly depend on the intrinsic characteristics of the exercise bout. Moreover, several variables, such as energy balance and environmental factors, can further influence these metabolic and endocrine adaptive processes. Therefore, the overall effect of altitude and PA on endocrine functions has been studied for many years, although this research field still hides numerous methodological pitfalls that prevent final conclusions from being drawn.
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Skeletal muscle wasting has been shown to be a mechanism by which humans are able to adapt to extreme altitude. Nonetheless, the literature is conflicting regarding the altitude or time point at which this phenomenon starts to occur. Using the metric recently suggested by Garvivan-Lewis et al. (8), we propose an hypoxic dose of 5000 km·h as the cut-off point above which hypoxia-induced muscle atrophy starts to develop. As such, we suggest that both elevation and hours of altitude exposure should be incorporated in future studies unraveling hypoxic regulation of muscle mass.
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This study introduced by resolving GI associated disorder three apparatuses and two medicines which are specially developed for making the life easier at high altitudes. The apparatuses included a convenient time saving operation, cost saving and efficient kerosene stove which causes very little pollution; A sprouts making device to work at low pressure and temperature and curd making machine to work again under extreme conditions of temperature and pressure. The medicines that are ready for use after rigorous testing and clinical trials are: tablets for nausea and vomiting and pro-biotic added antibiotic target release oral formulation tablets. These innovations are sure to improve the life of people at high altitudes.
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The gut microbiota is involved in host responses to high altitude. However, the dynamics of intestinal microecology and their association with altitude-related illness are poorly understood. Here, we used a rat model of hypobaric hypoxia challenge to mimic plateau exposure and monitored the gut microbiome, short-chain fatty acids (SCFAs), and bile acids (BAs) over 28 d. We identified weight loss, polycythemia, and pathological cardiac hypertrophy in hypoxic rats, accompanied by a large compositional shift in the gut microbiota, which is mainly driven by the bacterial families of Prevotellaceae, Porphyromonadaceae, and Streptococcaceae. The aberrant gut microbiota was characterized by increased abundance of the Parabacteroides, Alistipes, and Lactococcus genera and a larger Bacteroides to Prevotella ratio. Trans-omics analyses showed that the gut microbiome was significantly correlated with the metabolic abnormalities of SCFAs and BAs in feces, suggesting an interaction network remodeling of the microbiome-metabolome after the hypobaric hypoxia challenge. Interestingly, the transplantation of fecal microbiota significantly increased the diversity of the gut microbiota, partially inhibited the increased abundance of the Bacteroides and Alistipes genera, restored the decrease of plasma propionate, and moderately ameliorated cardiac hypertrophy in hypoxic rats. Our results provide an insight into the longitudinal changes in intestinal microecology during the hypobaric hypoxia challenge. Abnormalities in the gut microbiota and microbial metabolites contribute to the development of high-altitude heart disease in rats.
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Fullerton, Zackery S., Benjamin D. McNair, Nicholas A. Marcello, Emily E. Schmitt, and Danielle R. Bruns. Exposure to high altitude promotes loss of muscle mass that is not rescued by metformin. High Alt Med Biol. xx:xxx-xxx, 2022. Background: Exposure to high altitude (HA) causes muscle atrophy. Few therapeutic interventions attenuate muscle atrophy; however, the diabetic drug, metformin (Met), has been suggested as a potential therapeutic to preserve muscle mass with aging and obesity-related atrophy. The purpose of the present study was to test the hypothesis that HA would induce muscle atrophy that could be attenuated by Met. Methods: C57Bl6 male and female mice were exposed to simulated HA (∼5,200 m) for 4 weeks, while control (Con) mice remained at resident altitude (∼2,180 m). Met was administered in drinking water at 200 mg/(kg·day). We assessed muscle mass, myocyte cell size, muscle and body composition, and expression of molecular mediators of atrophy. Results: Mice exposed to HA were leaner and had a smaller hind limb complex (HLC) mass than Con mice. Loss of HLC mass and myocyte size were not attenuated by Met. Molecular markers for muscle atrophy were activated at HA in a sex-dependent manner. While the atrophic regulator, atrogin, was unchanged at HA or with Met, myostatin expression was upregulated at HA. In female mice, Met further stimulated myostatin expression. Conclusions: Although HA exposure resulted in loss of muscle mass, particularly in male mice, Met did not attenuate muscle atrophy. Identification of other interventions to preserve muscle mass during ascent to HA is warranted.
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Small-bowel absorption was studied using the xylose absorption test in 16 patients with varying degrees of arterial oxygen desaturation due to either congenital heart disease or chronic lung disease. Xylose absorption was decreased in the cases with more severe desaturation. The correlation of xylose absorption with arterial saturation was significant. In nine cases hypoxia was relieved by either oxygen administration or surgery. Repeat testing showed an increase in xylose absorption in every case, the mean increase being 11.7%, which was statistically significant.
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We tested the hypothesis that exposure to altitude decreases reliance on free fatty acids (FFA) as substrates and increases dependency on blood glucose. Therefore, the effects of exercise, hypobaric hypoxia, and altitude acclimatization on FFA, glycerol and net glucose uptake and release [= 2(leg blood flow)(arteriovenous concentration)] and on fatty acid (FA) consumption by the legs (= 3 x glycerol release + FFA uptake) were measured. Because sympathetic responses have been implicated, we utilized nonspecific beta-blockade and observed responses to exercise, altitude, and altitude acclimatization. We studied six healthy beta-blocked men (beta) and five matched controls (C) during rest and cycle ergometry exercise (88 W) at 49% of sea-level (SL) peak O2 uptake at the same absolute power output on acute altitude exposure (A1; barometric pressure = 430 Torr) and after 3 wk of chronic altitude exposure to 4,300 m (A2). During exercise at SL, FA consumption rates increased (P < 0.05). On arrival at 4,300 m, resting leg FFA uptake and FA consumption rates were not significantly different from those at SL. However, after acclimatization to altitude, at rest leg FA consumption decreased to essentially zero in both C and beta groups. During exercise to altitude after acclimatization, leg FA consumption increased significantly, but values were less than at SL or A1 (P < 0.05), whereas glucose uptake increased relative to SL values. Furthermore, beta-blockade significantly increased glucose uptake relative to control. We conclude that 1) chronic altitude exposure decreases leg FA consumption during rest and exercise; 2) relative to SL FFA uptake decreases while glucose uptake increases during exercise at altitude; and 3) beta-blockade potentiates these effects.
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The objectives of the study were to determine total energy intakes, distribution of energy derived from the macronutrients, and the effects of increasing altitudes on energy and macronutrient consumption during exposure to high altitudes. High fat, low carbohydrate diets (35% and 50% of energy, respectively) or low fat, high carbohydrate diets (20% and 65% of energy, respectively) were provided to two groups of subjects for a 3-wk period. Groups then consumed the alternate diet for 3 wk, followed by a return to the original diet for the remaining 3 wk of the study. Free choice of individual items and amounts within each diet was permitted. Intake of food and fluid was determined by means of monitored entries in daily food records. Five subjects remained at Base Camp (5300 m) and 10 subjects climbed to altitudes up to and including the summit of Mt. Everest (8848 m). Subjects consumed an average of 10.22 +/- 4.57 MJ/d (2442 +/- 1092 kcal) energy while at Base Camp, with climbers consuming significantly more than Base Camp personnel [11.89 +/- 4. 88 vs. 7.87 +/- 2.98 MJ/d (2841 +/- 1167 vs. 1881 +/- 713 kcal/d), P </= 0.0001]. There was a significant decline in energy consumption at increasing altitudes (P = 0.022), but no shift in distribution of energy provided from fat, carbohydrate or protein (P > 0.05). Contrary to previous reports, subjects in this study did not shift their food selections away from the high fat items towards high carbohydrate items.
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The objectives of the study were to determine regional changes in body composition, energy expenditure by means of doubly labeled water, and net energy balance during exposure to high and extreme altitudes (5,300-8,848 m). This study focuses on a subset of subjects who consumed the doubly labeled water (three base camp personnel and seven climbers). Regional body composition was determined by measuring skinfold thicknesses and circumferences at 10 different sites on the body. Energy expenditure was measured by doubly labeled water excretion. Discrepancies between actual energy expenditure and data obtained from diet records and body weight changes suggested a chronic underreporting of dietary energy intake, especially by those subjects who reached the highest altitudes. This underreporting may be due in part to diminished cognition or to a preferential focus on survival, rather than on filling out diet records accurately. Mean adjusted dietary intakes were 10.50 +/- 0. 65 MJ/d (2510 +/- 155 kcal/d) for those who remained at base camp, and 20.63 +/- 6.56 MJ/d (4931 +/- 1568 kcal/d) for those who climbed above base camp. Energy expenditure averaged 2.5-3.0 times sea level resting energy expenditure. Differential changes in regional body composition suggested a preferential loss of fat mass and a relative sparing of muscle mass, despite insufficient energy intake to maintain body weight.
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To test the hypotheses that prolonged exposure to moderately high altitude increases the energy requirement of adequately fed women and that the sole cause of the increase is an elevation in basal metabolic rate (BMR), we studied 16 healthy women [21.7 +/- 0.5 (SD) yr; 167.4 +/- 1.1 cm; 62.2 +/- 1.0 kg]. Studies were conducted over 12 days at sea level (SL) and at 4,300 m [high altitude (HA)]. To test that menstrual cycle phase has an effect on energetics at HA, we monitored menstrual cycle in all women, and most women (n = 11) were studied in the same phase at SL and HA. Daily energy intake at HA was increased to respond to increases in BMR and to maintain body weight and body composition. Mean BMR for the group rose 6.9% above SL by day 3 at HA and fell to SL values by day 6. Total energy requirement remained elevated 6% at HA [ approximately 670 kJ/day (160 kcal/day) above that at SL], but the small and transient increase in BMR could not explain all of this increase, giving rise to an apparent "energy requirement excess." The transient nature of the rise in BMR may have been due to the fitness level of the subjects. The response to altitude was not affected by menstrual cycle phase. The energy requirement excess is at present unexplained.
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Physical performance of sea-level (SL) residents acutely exposed to altitude (ALT) is diminished and may improve somewhat with ALT acclimatization. A large reduction in lean body mass (LBM), due to severe energy intake deficit during the first 21 d of ALT (4300 m) acclimatization, will adversely affect performance. At ALT, 10 men received a deficit (DEF) of 1500 kcal x d(-1) below body weight (BW) maintenance requirements and 7 men received adequate (ADQ) kcal x d(-1) to maintain BW. Performance was assessed by: 1) maximal oxygen uptake (VO2max); 2) time to complete 50 cycles of a lift and carry task (L+C); 3) number of one-arm elbow flexions (10% BW at 22 flexions x min(-1); and 4) adductor pollicis (AP) muscle strength and endurance time (repeated 5-s static contractions at 50% of maximal force followed by 5-s rest, to exhaustion). Performance and body composition (using BW and circumference measures) were determined at SL and at ALT on days 2 through 21. At SL, there were no between-group differences (p > 0.05) for any of the performance measures. From SL to day 21 at ALT, BW and LBM declined by 6.6 +/- 3 kg and 4.6 kg, respectively, for the DEF group (both p < 0.01), but did not change (both p > 0.05) for the ADQ group. Performance changes from day 2 or 3 to day 20 or 21 at ALT were as follows (values are means +/- SD): VO2max (ml x min(-1)): DEF = +97 +/- 237, ADQ = +159 +/- 156; L + C (s): DEF = -62 +/- 35*, ADQ = -35 +/- 20* (*p < 0.05; improved from day 3); arm flex (reps): DEF = -2 +/- 7, ADQ = +2 +/- 8; AP endurance (min): DEF = +1.4 +/- 2, ADQ = + 1.9 +/- 2; AP strength (kg): DEF = -0.7 +/- 4, ADQ = -1.2 +/- 2. There were no differences in performance between groups. A significant BW and LBM loss due to underfeeding during the first 21 d of ALT acclimatization does not impair physical performance at ALT.
Article
Altitude exposure may lead to considerable weight loss. Most reports, showing weight losses of 3% in 8 days at 4300m and up to 15% after 3 months at 5300 to 8000m, appear to indicate that this weight loss is a function of both absolute altitude and the duration of exposure. Based on the available scientific evidence to date, it is concluded that altitude weight loss is because of an initial loss of water and subsequent loss of fat and muscle mass due to malnutrition. Up to 5500m, malabsorption of macronutrients does not occur. Up to altitudes around 5000m, weight loss from a reduction of fat and muscle appears to be avoidable by maintaining adequate dietary intake. Primary anorexia, lack of comfort and palatable food, detraining, and possibly direct effects of hypoxia on protein metabolism seem inevitably to lead to weight loss during longer exposures at higher altitudes. To minimise losses, it is advisable to acclimatise properly, reduce the length of stay at extreme altitude as much as possible and maintain a high and varied nutrient intake. With sojourns at intermediate altitude for training purposes, adequate energy intake should be maintained taking into account the decrease in aerobic training intensity and the increase in basal metabolic rate that ensue from the hypoxic environment.
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To investigate the effects of high altitude on intestinal function, the absorption and permeation of nonmetabolizable carbohydrates were measured in 14 volunteers (median age 21 yr, range 19-37 yr) at sea level in Oxford, UK; at 1,050 m in Nepal; at 5,570 m after 5 days at > 5,500 m; and at 5,730 m after 11 days at > 5,500 m. Body weight decreased 5.7 +/- 1.19 kg from sea level to 5,570 m (P < 0.001 by paired t test) despite 72-h dietary records showing no change in energy intake. Absorption of carbohydrates by mediated transport was measured by urinary xylose and 3-O-methyl-D-glucose excretion. Xylose excretion (%oral dose) decreased from 31.4 +/- 4.5% to 20.7 +/- 4.5% (P < 0.001) and 3-O-methyl-D-glucose excretion decreased from 39.7 +/- 6.1 to 33.7 +/- 7.0% (P = 0.003) from sea level to 5,730 m. Monosaccharide permeation measured by L-rhamnose excretion decreased from 11.3 +/- 2.5 to 6.2 +/- 2.0% (P = 0.001). Intestinal permeability, a measure of barrier function (ratio of lactulose to L-rhamnose), increased from 0.036 +/- 0.014 at sea level to 0.084 +/- 0.042 at 1,050 m (P = 0.006), possibly due to infective enteropathy after arrival in Nepal, but reverted to normal (0.045 +/- 0.013; P = 0.062) at 5,730 m. Absorption of all carbohydrates returned to normal after return to the UK. This study showed that a decrease in mediated (D-xylose or 3-O-methyl-D-glucose) and diffusional (L-rhamnose) monosaccharide absorption occurs at high altitude but that intestinal permeability at 5,730 m is unchanged.
Article
We hypothesized that progressive loss of body mass during high-altitude sojourns is largely caused by decreased food intake, possibly due to hypobaric hypoxia. Therefore we assessed the effect of long-term hypobaric hypoxia per se on appetite in eight men who were exposed to a 31-day simulated stay at several altitudes up to the peak of Mt. Everest (8,848 m). Palatable food was provided ad libitum, and stresses such as cold exposure and exercise were avoided. At each altitude, body mass, energy, and macronutrient intake were measured; attitude toward eating and appetite profiles during and between meals were assessed by using questionnaires. Body mass reduction of an average of 5 +/- 2 kg was mainly due to a reduction in energy intake of 4.2 +/- 2 MJ/day (P < 0.01). At 5,000- and 6,000-m altitudes, subjects had hardly any acute mountain sickness symptoms and meal size reductions (P < 0.01) were related to a more rapid increase in satiety (P < 0.01). Meal frequency was increased from 4 +/- 1 to 7 +/- 1 eating occasions per day (P < 0. 01). At 7,000 m, when acute mountain sickness symptoms were present, uncoupling between hunger and desire to eat occurred and prevented a food intake necessary to meet energy balance requirements. On recovery, body mass was restored up to 63% after 4 days; this suggests physiological fluid retention with the return to sea level. We conclude that exposure to hypobaric hypoxia per se appears to be associated with a change in the attitude toward eating and with a decreased appetite and food intake.
Article
We hypothesized that hypoxia decreases energy intake and increases total energy requirement and, additionally, that decreased barometric pressure increases total water requirement. Energy and water balance was studied over 31 days in a hypobaric chamber at 452-253 Torr (corresponding to 4,500-8,848 m altitude), after 7 days acclimatization at 4,350 m. Subjects were eight men, age 27+/-4 years (mean+/-SD), body mass index 22.9+/-1.5 kg/m2. Food and water intake was measured with weighed dietary records, energy expenditure and water loss with labelled water. Insensible water loss was calculated as total water loss minus urinary and faecal water loss. Energy intake at normoxia was 13.6+/-1.8 MJ/d. Energy intake decreased from 10.4+/-2.1 to 8.3+/-1.9 MJ/d (P<0.001) and energy expenditure from 13.3+/-1.6 to 12.1+/-1.8 MJ/d (P<0.001) over the first and second 15-day intervals of progressive hypoxia. Absolute insensible water loss did not change (1.67+/-0.26 and 1.66+/-0.37 l/d), however, adjusted for energy expenditure it increased with ambient pressure reduction (P<0.05). In conclusion, hypoxia induced a negative energy balance, mainly by a reduction of energy intake. Overall insensible water loss was unchanged because the increase in respiratory evaporative water loss was counterbalanced by a decrease in metabolic rate that probably limited the hypoxia-induced increase in ventilation.
Article
The aims of the present study were to measure the satiety neuropeptide cholecystokinin (CCK) in humans at terrestrial high altitude to investigate its possible role in the pathophysiology of anorexia, cachexia, and acute mountain sickness (AMS). Nineteen male mountaineers aged 38 +/- 12 years participated in a 20 +/- 5 day trek to Mt. Kanchenjunga basecamp (BC) located at 5,100 m, where they remained for 7 +/- 5 days. Subjects were examined at rest and during a maximal exercise test at sea-level before/after the expedition (SL1/SL2) and during the BC sojourn. There was a mild increase in Lake Louise AMS score from 1.1 +/- 1.2 points at SL1 to 2.3 +/- 2.3 points by the end of the first day at BC (P < 0.05). A marked increase in resting plasma CCK was observed on the morning of the second day at BC relative to sea-level control values (62.9 +/- 42.2 pmol/L(-1) vs. SL1: 4.3 +/- 8.3 pmol/L(-1), P < 0.05 vs. SL2: 26.5 +/- 25.2 pmol/L(-1), P < 0.05). Maximal exercise increased CCK by 78.5 +/- 24.8 pmol/L(-1), (P < 0.05 vs. resting value) during the SL1 test and increased the plasma concentration of non-esterified fatty acids and glycerol at BC (P < 0.05 vs. SL1/SL2). The CCK response was not different in five subjects who presented with anorexia on Day 2 compared with those with a normal appetite. While there was no relationship between the increase in CCK and AMS score at BC, a more pronounced increase in resting CCK was observed in subjects with AMS (> or =3 points at the end of Day 1 at BC) compared with those without (+98.9 +/- 1.4 pmol/L(-1) vs. +67.6 +/- 37.2 pmol/L(-1), P < 0.05). Caloric intake remained remarkably low during the stay at BC (8.9 +/- 1.4 MJ.d(-1)) despite a progressive decrease in total body mass (-4.5 +/- 2.1 kg after 31 +/- 13 h at BC, P < 0.05 vs. SL1/SL2), which appeared to be due to a selective loss of torso adipose tissue. These findings suggest that the satiogenic effects of CCK may have contributed to the observed caloric deficit and subsequent cachexia at high altitude despite adequate availability of palatable foods. The metabolic implications of elevated CCK in AMS remain to be elucidated.
Article
Many studies have shown that subjects lose significant amounts of body mass, fat mass as well as fat-free mass, during a climb to and/or a stay at high altitude. Altitude-induced weight loss is mainly caused by malnutrition due to hypoxia-related satiety, independent of acute mountain sickness.