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Macronutrient profile affects diet-induced thermogenesis and energy intake

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Abstract

The diet composition can interfere directly in the energy homeostase. In the energy metabolism, the oxidation pathway and diet-induced thermogenesis are differentiated by diet macronutrients proportion. In this respect, the high-protein diet is the most thermogenic, compared to high-carbohydrate and high-lipid diets, while high-carbohydrate diet appears to increase the thermogenic effect more than high-lipid diet, but the studies are controversies. Towards energy intake, it can stimulate or inhibit the energy intake, according to the foods palatability, satiation and satiety degree, related to diet carbohydrate, protein and lipid content. A hierarchy has been observed for the satiating efficacies of the macronutrients protein, carbohydrate and fat, with protein as most satiating and fat as least satiating. In general, there are discrepancies between studies about the regulatory role of macronutrients in the components of energy expenditure and intake, due the methodological differences in the subjects, exposition time for diet, energy density, and total energy content. The present work seeks to analyze the more consistent scientific evidences toward the modulator role of diet composition on the diet induced thermogenesis and energy intake, for better understanding of obesity prevention and control by dietetic intervention.

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... After the adjustments, NCDP showed a significantly higher DIT and iAUC values (kcal 9 3 h) after lunch, compared with DCNP. Some authors believe that the thermic effect of protein may remains longer than 6-7 h, which explains these findings [34][35][36]. The highest thermic effect of protein is attributed to the high ATP cost for protein synthesis, urea production, and gluconeogenesis [34,36,37]. ...
... During the day, while carbohydrate is ingested, the glycogen stores remain saturated and, then, most of the carbohydrate is oxidized. On the other hand, in nocturnal fasting periods, glycogen stores start to be used, thus reducing the level of carbohydrate oxidation for their preservation [35,38]. ...
Article
Purpose: To evaluate the effects of two dietary patterns in which carbohydrates and proteins were eaten mostly at lunch or dinner on body weight and composition, energy metabolism, and biochemical markers in overweight/obese men. Methods: Fifty-eight men (30.0 ± 7.4 years; 30.8 ± 2.4 kg/m(2)) followed a covert hypocaloric balanced diet (-10 % of daily energy requirements) during 8 weeks. Subjects were randomly assigned to three groups: control diet (CT); diurnal carbohydrate/nocturnal protein (DCNP); and nocturnal carbohydrate/diurnal protein (NCDP). Main analyzed outcomes were weight loss, body composition, diet-induced thermogenesis (DIT), and glucose/lipid profile. Results: In all groups, a significant decrease in body weight, BMI, and fat mass (kg and %) was verified, without differences between groups. Interestingly, within group analyses showed that the fat-free mass (kg) significantly decreased in NCDP and in CT after 8-week intervention, but not in DCNP. A detrimental increase in fasting glucose, insulin, and homeostasis model assessment of insulin resistance (HOMAIR) was verified only in DCNP, while NCDP and CT groups presented a non-significant reduction. Moreover, significant differences between DCNP and the other groups were detected for fasting insulin and HOMAIR. After the adjustments, NCDP presented a significantly higher DIT and energy expenditure after lunch, compared with DCNP, but after dinner, there were no differences among groups. Conclusion: Eating carbohydrates mostly at dinner and protein mostly at lunch within a hypocaloric balanced diet had similar effect on body composition and biochemical markers, but higher effect on DIT compared with control diet. Moreover, eating carbohydrates mostly at lunch and protein mostly at dinner had a deleterious impact on glucose homeostasis.
... There is general agreement that protein has greater effect on diet-induced thermogenesis (DIT) than carbohydrate and fat 1,[13][14][15][16][17] . Besides, dietary fiber improves satiety and reduces hunger sensation 15,[18][19][20][21] . ...
... There is general agreement that protein has greater effect on diet-induced thermogenesis (DIT) than carbohydrate and fat 1,[13][14][15][16][17] . Besides, dietary fiber improves satiety and reduces hunger sensation 15,[18][19][20][21] . Since peanuts is one of the highest protein contents nuts (≈24%), and it also has ≈8% of dietary fiber, its consumption may contribute to appetite control and to increase DIT 3,5 . ...
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Background: Evidences suggest that nuts consumption can improve energy metabolism. Purpose: This study aimed to compare the effects of acute ingestion of high-oleic and conventional peanuts on appetite, food intake, and energy metabolism in overweight and obese men. Methods: Seventy one subjects (29.8 ± 2.4 kg/m2) were assigned to the groups: control (CT, n = 24); conventional peanuts (CVP, n = 23); high-oleic peanuts (HOP, n = 24). Subjects consumed 56 g of peanuts (CVP and HOP) or control biscuits (CT) after overnight fasting. Thereafter, energy metabolism was evaluated over 200 minutes, during which diet-induced thermogenesis (DIT) and substrate oxidation were analyzed. Appetite sensation was recorded for 3 hours. Statistical analyses were performed using the SAS software considering 5% as the significance level. Results: Postprandial energy expenditure and DIT were significantly higher in HOP than in CVP. Substrate oxidation did not differ between groups. Only HOP presented score below 100 indicating incomplete compensation. CT and CVP showed a complete caloric compensation (scores > 100). Regarding appetite sensation, CVP group felt less "full" than HOP and CT. After 3 hours, satiety score of CVP returned to baseline, whereas HOP and CT remained significantly higher. Hunger scores returned to baseline in CVP and CT and they were maintained significantly lowered in HOP. Conclusion: High-oleic peanuts contributed to higher DIT, higher sensation of fullness and incomplete compensation for energy intake compared to conventional peanuts and may be useful to dietary intervention to reduce body weight.
... In addition the body fat storage may have been limited as a result of the unsaturated fatty acids being oxidized. Unsaturated fats and have a greater thermogenic effect [43] and are more readily oxidised [44] than saturated fatty acids making them less readily stored in the adipose tissue. Further, peanut consumption for 8 weeks has elicited a small (5%) but significant increment in resting energy expenditure in obese individuals [40]. ...
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Epidemiological evidence indicates an inverse association between nut consumption and obesity, inflammation, hyperlipidaemia and glucose intolerance. We investigated effects of high oleic peanut consumption vs. a nut free diet on adiposity and cardio-metabolic risk markers. In a randomised cross-over design, 61 healthy subjects (65 ± 7 years, body mass index (BMI) 31 ± 4 kg/m²) alternated either high oleic peanuts (15%-20% of energy) or a nut free diet for 12 weeks. Body composition and mass, waist circumference, C-reactive protein (CRP), lipids, glucose and insulin were assessed at baseline and after each phase. Repeated measures analysis of variance (ANOVA) compared the two diets. Consistent with other nut studies, there were no differences in lipids, CRP, glucose and insulin with peanut consumption. In contrast, some reports have demonstrated benefits, likely due to differences in the study cohort. Energy intake was 10% higher (853 kJ, p < 0.05), following peanut consumption vs. control, attributed to a 30% increase in fat intake (p < 0.001), predominantly monounsaturated (increase 22 g, p < 0.05). Despite greater energy intake during the peanut phase, there were no differences in body composition, and less than predicted increase (0.5 kg) in body weight for this additional energy intake, possibly due to incomplete nutrient absorption and energy utilisation.
... Similarly, the consumption of foods with highprotein content can also increase REE and DIT due to mechanisms inherent to the physiological process of protein oxidation. This nutrient requires more energy for metabolic processes such as deamination, gluconeogenesis, and urea formation (Hermsdorff et al. 2007;Gilbert et al. 2011). ...
Article
Nuts are high-energy density foods and are associated with beneficial effects on health, including weight control. Effects on resting energy expenditure, respiratory quotient, and diet-induced thermogenesis are suggested mechanisms behind the effects of nuts consumption on weight control. Thus, we revised the randomised clinical trials that assessed acute and chronic nuts consumption effects on energy metabolism. Walnuts (22.1 g to 56 g) consumption appears to modulate energy metabolism markers differently depending on the dose and profile of the evaluated subject. In its turn, 56 g of high-oleic peanuts increased postprandial energy expenditure and thermic effect of food after three hours postprandial compared to consumption of conventional peanuts. Almonds, hazelnuts, peanuts, and a mix of nuts were the nuts studies in the chronic studies, which does not seem to influence energy metabolism markers. Further studies are needed to elucidate the effects of other types of nuts consumption on energy metabolism.
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Inpatient metabolic studies of human subjects were performed to obtain data on important nutritional issues. It was shown that wide variations in the ratio of carbohydrate to fat do not alter total 24-h energy need. Studies of the fatty acid composition of plasma low-density lipoproteins during low-fat feeding indicated that there can be considerable lipogenesis from carbohydrate in humans during isoenergetic feeding. The energy cost of this conversion must be small or be counterbalanced by other changes in energy metabolism because measured energy need was unaltered by fat-to-carbohydrate ratios. Energy need was, however, markedly varied by changes in body weight. Subjects at their usual body weights who had experimentally induced increases in body weight became inefficient and required a higher energy intake for weight maintenance. The reverse occurred with a reduction in body weight. The set point at which energy storage is defended is clearly different in obese persons.
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To investigate physiological differences between habitual high-fat (HF) and low-fat (LF) consumers, which could influence the balance between energy expenditure and energy intake, and the potential for weight gain. 16 young, lean males (eight HF and eight LF consumers; % energy from fat 44.3 and 32.0, respectively). Habitual dietary variables (from FFQ), body mass index (BMI), body fat % (measured by impedance), resting metabolic rate (RMR) (indirect calorimetry), substrate oxidation and basal heart rate, postprandial thermogenesis and heart rate in response to a high-fat (low carbohydrate (CHO)) and high-CHO (low fat) challenge. HF and LF (selected for their intake of fat) did not differ significantly in BMI or % body fat. HF had a significantly higher RMR (1624 vs 1455 kcal/d) and basal heart rate (66 vs 57 bpm) than LF. Differences in oxygen utilisation and heart rate were maintained over a 180 min period, following the high-fat and high-CHO challenge meals. HF had a significantly lower resting respiratory quotient (RQ) than LF and the differences in average RQ were significant over the 180 min examination period. HF had a significantly lower RQ response to the high fat (low CHO) than to the high CHO (low fat) challenge; this effect was not observed in LF. HF had higher total energy intake than LF and a higher absolute (but not %) intake of protein. Significant differences in basal energy expenditure and fat oxidation between habitual HF and LF consumers have been observed. The contributions of energy intake and protein intake (g not %) remain to be determined. In this particular group of subjects (young adult males) a high energy intake characterised by a large fat component is associated with metabolic adaptations which could offset the weight inducing properties of a high-fat diet. These physiological differences may be important when considering the relationship between dietary-fat and obesity.
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In this review, we consider two hypotheses which could explain why high-fat foods are overeaten. The first hypothesis is that fat is overeaten because it affects satiety and satiation less than carbohydrate. In several studies which have evaluated the effects of fat on satiety and satiation, fat differed little from carbohydrate when both the palatability and energy density of the test foods were matched. Therefore it is unlikely that the effects of fat on satiety or satiation provide the primary explanation for why it is overeaten. The second hypothesis is that the high energy density of fat facilitates its overconsumption. Support for this view comes from recent studies in which energy density significantly influenced intake when both the macronutrient content and palatability of the test foods were matched. For example, when individuals were fed diets varying in energy density and could eat as much food as they liked, they ate the same amount of food (by weight) so energy intake varied directly with energy density. Furthermore, when participants consumed foods of low energy density, they felt satisfied, despite reductions in energy intake. These findings show that energy density is a key determinant of energy intake in that cognitive, behavioral, and sensory cues related to the volume or weight of food consumed can interact with or override physiological cues associated with food intake.
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Assessment of a possible relationship between perception of satiety and diet-induced thermogenesis, with different macronutrient compositions, in a controlled situation over 24 h. Two diets with different macronutrient compositions were offered to all subjects in randomized order. The study was executed in the respiration chambers at the department of Human Biology, Maastricht University. Subjects were eight females, ages 23-33 y, BMI 23+/-3 kg/m2, recruited from University staff and students. Subjects were fed in energy balance, with protein/carbohydrate/fat: 29/61/10 and 9/30/61 percentage of energy, with fixed meal sizes and meal intervals, and a fixed activity protocol, during 36 h experiments in a respiration chamber. The appetite profile was assessed by questionnaires during the day and during meals. Diet induced thermogenesis was determined as part of the energy expenditure. Energy balance was almost complete, with non-significant deviations. Diet-Induced-Thermogenesis (DIT) was 14.6+/-2.9%, on the high protein/carbohydrate diet, and 10.5+/-3.8% on the high fat diet (P < 0.01). With the high protein/high carbohydrate diet, satiety was higher during meals (P < 0.001; P < 0.05), as well as over 24 h (P < 0.001), than with the high fat diet. Within one diet, 24 h DIT and satiety were correlated (r = 0.6; P < 0.05). The difference in DIT between the diets correlated with the differences in satiety (r = 0.8; P < 0.01). In lean women, satiety and DIT were synchronously higher with a high protein/high carbohydrate diet than with a high fat diet. Differences (due to the different macronutrient compositions) in DIT correlated with differences in satiety over 24 h.
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The present study investigated metabolic responses to fat and carbohydrate ingestion in lean male individuals consuming an habitual diet high or low in fat. Twelve high-fat phenotypes (HF) and twelve low-fat phenotypes (LF) participated in the study. Energy intake and macronutrient intake variables were assessed using a food frequency questionnaire. Resting (RMR) and postprandial metabolic rate and substrate oxidation (respiratory quotient; RQ) were measured by indirect calorimetry. HF had a significantly higher RMR and higher resting heart rate than LF. These variables remained higher in HF following the macronutrient challenge. In all subjects the carbohydrate load increased metabolic rate and heart rate significantly more than the fat load. Fat oxidation (indicated by a low RQ) was significantly higher in HF than in LF following the fat load; the ability to oxidise a high carbohydrate load did not differ between the groups. Lean male subjects consuming a diet high in fat were associated with increased energy expenditure at rest and a relatively higher fat oxidation in response to a high fat load; these observations may be partly responsible for maintaining energy balance on a high-fat (high-energy) diet. In contrast, a low consumer of fat is associated with relatively lower energy expenditure at rest and lower fat oxidation, which has implications for weight gain if high-fat foods or meals are periodically introduced to the diet.
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This dietary trial was designed to evaluate the effect of an experimental short-term fasting period followed by a high-carbohydrate meal on energy expenditure, thermogenesis, and sympathetic nervous system activity in normal (body mass index < 25 kg/m(2)) and overweight (body mass index > 27 kg/m(2)) men who were healthy, non-diabetic or with no other endocrine disease, non-smokers, not taking oral prescription medications, and with a stable body weight for the previous 3 mo. Fasting and fed energy expenditures and diet-induced thermogenesis were measured after a high-carbohydrate meal in seven overweight and six lean young male subjects by indirect calorimetry. Heart rate, urinary excretion of catecholamines, serum glucose, and insulin were also measured over the experimental fasting (7.5 h) and postprandial (4 h) periods. After carbohydrate intake, overweight men showed a significantly higher energy production (kJ/kg of fat-free mass) than did lean individuals, and the diet-induced thermogenesis (percentage of energy intake) was positively correlated with body fat (kg), percentage of body fat, fat-free mass (kg), and fasting pre-meal serum insulin levels. Postprandial cumulative energy expenditure was directly associated with postprandial insulin response and with mean postprandial heart rate values. No significant differences in urinary catecholamines were found between lean and overweight men at basal conditions or during the study period. Overweight individuals showed similar short-term sympathetic nervous system responses induced by an experimental fasting period. Although diet-induced thermogenesis after carbohydrate intake was not statistically different between lean and overweight men, the postprandial insulin response and body fat content seemed to be involved in sympathetic nervous system activity.
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Abdominal obesity is associated with a blunted lipolytic response to fasting that may contribute to the preservation of adipose tissue mass. To further explore the pathophysiology of blunted lipolysis during fasting in obesity, we simultaneously measured lipolysis and distinct neuroendocrine regulatory hormones in abdominally obese and normal-weight (NW) women. Eight abdominally obese [x +/- SD body mass index (BMI; in kg/m(2)): 32.1 +/- 2.6] and 6 NW (BMI: 22.7 +/- 1.5) women were studied during the last 8 h of a 20-h fast. The glycerol appearance rate and the serum and plasma concentrations of insulin, leptin, cortisol, and growth hormone were measured regularly. At 13 h of fasting, the mean (+/-SD) glycerol appearance rate corrected for fat mass was greater in NW women than in obese women (7.2 +/- 1.0 and 5.1 +/- 0.6 micro mol.kg(-1).min(-1), respectively; P = 0.001). After a 20-h fast, lipolysis increased to 8.9 +/- 1.5 mmol.kg(-1).min(-1) in NW women (23%), whereas it did not change significantly in obese women (-2%). Fasting decreased insulin concentrations by approximately 30% in both groups, but it did not induce significant changes in leptin concentrations. Mean cortisol concentrations and urinary catecholamine excretion were comparable in both groups. However, mean plasma growth hormone concentrations were higher in NW women than in obese women (1.81 +/- 0.98 compared with 0.74 +/- 0.52 mU/L; P = 0.046). The relative change in lipolysis tended to correlate with mean plasma growth hormone concentrations (r = 0.515, P = 0.059). Abdominal obesity-associated hyposomatotropism may be involved in the blunted increase in lipolysis during fasting.
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Present-day human eating behaviour in industrialised society is characterised by the consumption of high-energy-density diets and often unstructured feeding patterns, largely uncoupled from seasonal cycles of food availability. Broadly similar patterns of feeding are found among advantaged groups in economically-emerging and developing nations. Such patterns of feeding are consistent with the evolutionary ecological understanding of feeding behaviour of hominids ancestral to humans, in that human feeding adaptations are likely to have arisen in the context of resource seasonality in which diet choice for energy-dense and palatable foods would have been selected by way of foraging strategies for the maximisation of energy intake. One hallmark trait of human feeding behaviour, complex control of food availability, emerged with Homo erectus (1.9 x 10(6)-200000 years ago), who carried out this process by either increased meat eating or by cooking, or both. Another key trait of human eating behaviour is the symbolic use of food, which emerged with modern Homo sapiens (100000 years ago to the present) between 25000 and 12000 years ago. From this and subsequent social and economic transformations, including the origins of agriculture, humans have come to use food in increasingly elaborate symbolic ways, such that human eating has become increasingly structured socially and culturally in many different ways.
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Human food intake is driven by necessity. We eat to live, but as Brillat-Savarin and others have noted throughout history, in affluent societies eating is a pleasure and becomes more than a means to an end. Eating signifies lifestyle choice and it has considerable meaning in our society beyond the acquisition of essential energy and nutrients. Thus, it is that the study of human food intake, particularly food choice, in contrast to food intake in other animals, tends to be skewed towards measures of behavioural, social and environmental influences rather than on precise physiological processes reflecting metabolism and nutrient partitioning. The dichotomy between physiological and psychological measures is a false one, since all behaviours are necessarily expressed through physiological systems. However, in the field of human food intake research the dichotomy refers to the divergent strands of interest in either psychological or physiological processes underlying intake and appetite. The present review considers both psychological and physiological measures in promoting our understanding of the human appetite system. The overall conclusion is that the burgeoning interest in identifying appetite suppressant drugs to combat obesity and in genotyping alongside behavioural phenotyping will close the gap between psychological and physiological perspectives on human food intake.
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Medium-chain triglyceride (MCT) consumption has been shown to increase energy expenditure (EE) and lead to greater losses of the adipose tissue in animals and humans. The objective of this research was to examine the relationship between body composition and thermogenic responsiveness to MCT treatment. Randomized, crossover, controlled feeding trial, with diets rich in either MCT or long-chain triglyceride (LCT) (as olive oil) for periods of 4 weeks each. A total of 19 healthy overweight men aged (x+/-s.e.m.) 44.5+/-2.5 y with a body mass index of 27.8+/-0.5 kg/m(2). EE and body composition were measured using indirect calorimetry and magnetic resonance imaging, respectively, at the baseline and end point of each feeding period. EE was measured for 30 min before consumption of a standard meal and for 5.5 h following the meal. Body weight (BW) decreased (P<0.05) by 1.03+/-0.25 kg with MCT consumption compared to 0.62+/-0.29 kg with LCT consumption. The difference in average EE between MCT and LCT consumptions was related to initial BW, such that men with lower initial BW had a greater rise in EE with MCT consumption relative to LCT on day 28 (r=-0.472, P=0.04) but not day 2 (r=-0.368, P=0.12). Similar results were obtained with fat oxidation on day 28 (r=-0.553, P=0.01). The greater rise in fat oxidation with MCT compared to LCT consumption on day 2 tended to be related to greater loss of BW after MCT vs LCT consumption (r=-0.4075, P=0.08). These data suggest that shunting of dietary fat towards oxidation results in diminished fat storage, as reflected by the loss of BW and subcutaneous adipose tissue. Furthermore, MCT consumption may stimulate EE and fat oxidation to a lower extent in men of greater BW compared to men of lower BW, indicative of the lower responsiveness to a rapidly oxidized fat by overweight men.International
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This study investigated whether the -3826 A-->G nucleotide variant of the uncoupling protein-1 (UCP1) gene is correlated with postprandial thermogenesis after a high fat meal in children. Healthy boys, aged 8-11 yr, were examined for resting energy expenditure and the thermic effect of a meal (TEM), which were measured by indirect calorimetry for 180 min after a high fat (70% fat, 20% carbohydrate, and 10% protein, providing 30% of the daily energy requirement) and a high carbohydrate meal (20% fat, 70% carbohydrate, and 10% protein). The sympatho-vagal activities were assessed by means of spectral analysis of the heart rate variability during the same period. Children were genotyped for UCP1 polymorphism by applying a PCR-restriction fragment length polymorphism using buccal samples. There was no reaction of sympathetic activity to the high carbohydrate meal in either the GG allele or the AA+AG group and no significant difference in TEM. However, after the high fat meal, sympathetic responses were found in both groups; further, the GG allele group showed significantly lower TEM than the AA+AG group. In conclusion, despite fat-induced sympathetic stimulation, GG allele carriers have a lowered capacity of TEM in response to fat intake, suggesting that such impaired UCP1-linked thermogenesis can have adverse effects on the regulation of body weight.
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To see whether a fat-rich (50%) evening meal promoted fat oxidation and a different spontaneous food intake on the following day at breakfast than a meal with a lower fat content (20%) in 10 prepubertal obese girls. The postabsorptive and postprandial (10.5 hours) energy expenditure after a low-fat (LF) (20% fat, 68% carbohydrate, 12% protein) and an isocaloric (2.1 MJ) and isoproteic high-fat (HF; 50% fat, 38% carbohydrate, 12% protein) meal were measured by indirect calorimetry. Fat oxidation was not significantly different after the two meals [LF, 31 +/- 9 vs. HF, 35 +/- 9 g/10.5 hours, p = not significant (NS)]. The girls oxidized 1.8 +/- 0.9 times more fat than that ingested (11.1 grams) with the LF meal vs. 0.3 +/- 0.3 times more fat than that ingested (27.1 grams) with the HF meal (p < 0.001). Carbohydrate oxidation was significantly higher after an LF than an HF meal (39 +/- 12 vs. 29 +/- 9 g/10.5 hours, p < 0,05). At breakfast, the girls spontaneously ingested a similar amount of energy (1.5 +/- 0.7 vs. 1.5 +/- 0.6 MJ, p = NS) and macronutrient proportions (fat, 23% vs. 26%, p = NS; protein, 9% vs. 10%; carbohydrate, 68% vs. 64%,) independently of their having eaten an HF or an LF dinner. An HF dinner did not stimulate fat oxidation, and no compensatory effect in spontaneous food intake was observed during breakfast the following morning. Cumulated total fat oxidation after dinner was higher than total fat ingested at dinner, but a much larger negative fat balance was observed after the LF meal. Spontaneous energy and nutrient intakes at breakfast were similar after LF and HF isocaloric, isoproteic dinners. This study points out the lack of sensitivity of short-term fat balance to subsequently readjust fat intake and emphasizes the importance of an LF meal to avoid transient positive fat imbalance.
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Objective: To compare the effects of two diets, which had their carbohydrates profile modified, on the energy metabolism of two groups of subjects: normal lean men and overweight ones. Methods: Two isoenergetic meal plans were used, to evaluate their effects in the energy expenditure of thirteen lean, and thirteen overweight men. Three regular meal preparations and their diet analogous preparations were used to compound the regular meal and the modified meal, respectively. Indirect calorimetry was used to estimate the energy expenditure. Results: Overweight subjects had a higher energy expenditure (p<0.01) and lower thermogenesis (p<0.01) comparing to lean subjects, independently of the meal tested. Modified meal was higher in complex carbohydrates and, independently of the group, its consumption caused rest respiratory quotient, rest energy expenditure, thremogenesis, and carbohydrate oxidation to be greater (p<0.05) than those observed when regular meal was consumed. Conclusion: Our results suggest that an isocaloric meal, higher in complex carbohydrate, can increase the respiratory coefficient, and, consequently, can increase thermogenesis and energy expenditure.
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The literature clearly documents the existence of nonshivering thermogenesis of adrenergic origin in adult humans. This thermogenesis is activated in cold exposed individuals, during the early phase of cooling, prior to shivering and equals to about 25% of the basal MR (0.29 W kg-1). This amount of heat can compensate for the heat loss from the body when the air temperature is about 5°C below the thermoneutral zone. Human nonshivering thermogenesis is probably based on thermogenic actions both of adrenaline and noradrenaline. Relative participation of adrenaline or noradrenaline in the thermogenic response is not known and the mode of action of the amines may differ. Adrenaline themogenesis, in contrast to noradrenaline thermogenesis, can be potentiated by cold adaptation to the level corresponding to the total capacity of β-adrenergic (isoprenaline) thermogenesis (0.58 W kg-1). Adrenaline thermogenesis is located in skeletal muscles and probably also in white fat. Diffused brown fat cells present in white fat pads may be also involved, however. Although several molecular mechanisms have been suggested, the discrete mode of catecholamine thermogenic action in organs other than the brown adipose tissue remains unknown. Participation of various subtypes of adrenoceptors and uncoupling proteins must be considered, although the direct evidence for their involvement in human adrenaline thermogenesis is still lacking. Thus the cellular mechanisms of human nonshivering thermogenesis may differ from those found in small mammals. Physiological regulatory mechanisms, namely changes in the blood flow, could be involved in inducing adrenergic thermogenesis in human muscle. Thus, the regulation of MR by catecholamines may not be solely dependent on biochemical mechanisms related to the uncoupling of oxidative phosphorylation but may also rely on physiological processes.
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International Journal of Obesity is a monthly, multi-disciplinary forum for papers describing basic, clinical and applied studies in biochemistry, genetics and nutrition, together with molecular, metabolic, psychological and epidemiological aspects of obesity and related disorders
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A response to the commentaries by Altman, Erikson and Moore, and an expansion of the original paper, giving data on bias at the 2001 UK general election.
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During the past 50 years, obesity has increasingly become a problem in Western societies. If low energy output by these individuals (i.e. lack of exercise) cannot be held totally accountable for this problem, then their energy input (i.e. appetite) must play a significant role. There are many elements that give rise to appetite disturbances and their effects on weight gain, weight loss or its maintenance. Previously, it was thought that emotional disturbances led to overeating and overweight; a theory that was supplanted later by the theory that physiological rather than psychological causes were to blame. Today, it is generally believed that appetite is controlled by the interaction of internal (genetic, physiological and chemical) and external (environmental and psychosocial) processes. The role of nutritional and dietary factors in controlling the expression of appetite are particularly important. Thus, appetite (hyperphagia or increased hunger) can be induced by changes in brain neurotransmitters and neuromodulators, altered liver metabolism, adjustments of the nutrient/sensory components of the diet, environmentally applied Stressors, the mental and behavioural imposition of dieting and the administration of various psychotropic medications. This review focuses on the role each of these mechanisms plays in the genesis and maintenance of appetite disturbances; the conclusion of each of these contributions is the same — control of appetite must be achieved in order to treat obesity, and to do this, control must be exerted via regulation of the food supply, cognitive methods, environmental adjustment or by pharmacological tools.
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The two-compartment model presented here suggests that weight maintenance can be achieved by a regulation of food intake geared primarily toward the maintenance of stable glycogen levels, rather than toward the preservation of the overall energy balance. This concept is reminiscent of the glucostatic theory of food intake regulation proposed by Mayer. It is viewed here as being linked to changes in the body's carbohydrate stores, which represent an integration of carbohydrate and lipid fluxes, rather than to changes in blood glucose levels, whose substantial variations during the day are dependent on various circumstantial events. The model illustrates that the fat to carbohydrate ratio of the diet may have considerable potential influence on steady state body composition, even though carbohydrates and fats are both able to meet the body's energy substrate requirements. It appears that failure of appropriately reducing the range within which glycogen levels are maintained when the diet's fat content rises will require an expansion of the adipose tissue mass to raise FFA levels and fat oxidation to a rate commensurate with the proportion of fat in the diet. Maintenance of glycogen reserves below their level of saturation is made less likely by the high palatability and ubiquitous availability of foods in affluent societies. Thus, one can understand the high incidence of obesity among populations consuming mixed diets with a relatively high fat content, without having to attribute this to some defect(s) in the mechanism(s) controlling food intake.
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Energy balance is the difference between metabolizable energy intake and total energy expenditure. Energy intake is difficult to measure accurately; changes in body weight, for example, are not a good measure of the adequacy of energy intake, because fluctuations in body weight are common even if the overall trend is toward weight loss. It is now customary to assess energy requirements indirectly from total energy expenditure. Total energy expenditure consists of basal metabolism, postprandial thermogenesis, and physical activity. Energy expenditure is related to both body weight and body composition. A reduction in total energy expenditure accompanies weight loss, because basal metabolic rate decreases with the loss of lean tissue mass. Similarly, with weight gain, there is an increase in basal metabolic rate, because lean tissue mass grows to support the increase in fat tissue mass. Excess energy intake over energy expenditure causes weight gain and an accompanying increase in total energy expenditure. Following a period of adaptation, total energy expenditure will match energy intake and body weight will stabilize at a higher level. This same relationship holds for weight loss. Respiratory quotient (measured in steady state) is an indication of the proportion of energy expenditure derived from fat and carbohydrate oxidation. Over long periods of time, fat balance is equivalent to energy balance, as an excess of fat intake over fat oxidation causes fat storage.
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This prospective study was designed to identify abnormalities of energy expenditure and fuel utilization which distinguish post-obese women from never-obese controls. 24 moderately obese, postmenopausal, nondiabetic women with a familial predisposition to obesity underwent assessments of body composition, fasting and postprandial energy expenditure, and fuel utilization in the obese state and after weight loss (mean 12.9 kg) to a post-obese, normal-weight state. The post-obese women were compared with 24 never-obese women of comparable age and body composition. Four years later, without intervention, body weight was reassessed in both groups. Results indicated that all parameters measured in the post-obese women were similar to the never-obese controls: mean resting energy expenditure, thermic effect of food, and fasting and postprandial substrate oxidation and insulin-glucose patterns. Four years later, post-obese women regained a mean of 10.9 kg while control subjects remained lean (mean gain 1.7 kg) (P < 0.001 between groups). Neither energy expenditure nor fuel oxidation correlated with 4-yr weight changes, whereas self-reported physical inactivity was associated with greater weight regain. The data suggest that weight gain in obesity-prone women may be due to maladaptive responses to the environment, such as physical inactivity or excess energy intake, rather than to reduced energy requirements.
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There is some evidence that the effects of carbohydrates and protein may differ with respect to satiety. This may depend in part on the different methods of preparing these nutrients for administration. Additional factors such as timing, different delays, differential metabolism and expectations of ingested foods may contribute to different outcomes of experiments investigating the satiating effects of macronutrients. Here, studies of the relative satiating effects of carbohydrates and protein are discussed followed by a methodological discussion of the reviewed studies. Finally, suggestions for methodological improvements are given which should allow future studies to investigate more clearly the mechanisms underlying satiety.
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To study the effect on the early (cephalic) phase of diet-induced thermogenesis (EDT) of palatable vs unpalatable food, in nonobese and obese man. Twenty-four nonobese volunteers and 19 obese clinic patients. A palatable, liquid formula meal of Ensure (1048 KJ, 450 ml), and of Ensure made unpalatable by addition of aqueous KCl, were sipped on nonconsecutive mornings. O2 consumption (ml/min) was measured before, and starting 30, 60 and 90 min after beginning the test meal, from which EDT was calculated as KJ/min. Palatability of the test meal significantly increased EDT (palatability effect, P = 0.004) but obesity status per se, did not affect EDT. Nevertheless, the effect of palatability on EDT was dependent on obesity status, being seen only in the nonobese. EDT was significantly greater in the nonobese after the palatable than the unpalatable meal: (mean +/- s.e.m.) 2.45 +/- 0.14 vs 1.83 +/- 0.14; P < 0.0001, but not in the obese: 1.93 +/- 0.28 vs 1.73 +/- 0.20; P < 0.21. Therefore only after the palatable meal was EDT less in the obese compared with the nonobese: P < 0.05. The threshold for the unpleasant taste of added KCI was 31% higher in the obese than the nonobese: 4.2 +/- 0.4 vs 3.2 +/- 0.2 [g KCI]; P < 0.025. The early (cephalic) phase of dietary thermogenesis (EDT) is significantly increased in the nonobese by palatability, but not in the obese, so that only after a palatable meal is EDT less, or 'deficient,' in the obese compared with the nonobese. Also, the obese have a higher threshold for the unpleasant taste of KCI (in Ensure) than the nonobese.
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To investigate the impact of a high-sucrose diet vs a high-starch and a high-fat diet on 14 d ad libitum energy intake, body weight, energy expenditure and sympathoadrenal activity. Food intake; body weight and composition (bioelectrical impedance); 24 h energy expenditure, substrate oxidation rates, spontaneous physical activity, heart rate and appetite sensations in a respiration chamber (VAS scores); plasma catecholamine concentration and blood pressure. Twenty normal-weight, healthy women, 9 post-obese (body mass index (BMI): 22.9 +/- 0.7 kg/m2) and 11 closely matched controls (BMI: 22.6 +/- 0.4 kg/m2). Average 14 d ad libitum energy intake was 13% and 12% lower on the starch diet compared with the sucrose and fat diets, respectively (P < 0.05). In both post-obese and normal-weight subjects, body weight and fat mass decreased significantly on the starch diet (by 0.7 +/- 0.2 kg and 0.4 +/- 0.1 kg, respectively, P < 0.05). No changes were observed on the fat or sucrose diets. After 14 d on the sucrose diet, 24 h energy expenditure as well as postprandial plasma adrenaline and noradrenaline concentrations, were significantly increased compared with the other two diets. Overall satisfy and palatability ratings were also highest on the sucrose diet. Intake of a 14-d ad libitum high-starch diet decreased energy intake and body weight compared with a high-fat or high-sucrose diet. The increased energy expenditure observed on the sucrose-rich diet can probably be explained both by the increased intake of energy and fructose (mainly from sucrose) on this diet.
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A regulatory increase in energy expenditure, induced by excess intake of palatable food (cafeteria diet), is well documented. It has also been shown that excess feeding by gastric intubation, fails to enhance thermogenesis, suggesting that the palatability of the food could have a role in producing this regulatory response. A study was planned to find out if a palatable diet pair-fed with standard laboratory chow would produce diet-induced thermogenesis (DIT) and if the brown adipose tissue (BAT) was involved in this process. Body weight gain, BAT activity and body temperature response to norepinephrine were measured in rats fed for 40 d either the standard laboratory pellets (control), a palatable high carbohydrate diet fed ad libitum and the same palatable diet but fed in restricted amounts to match the intake of the control group. It was found that palatable food either fed ad libitum or pair-fed, increased DIT and reduced food efficiency (which is the body weight gain per 100 kj of food consumed). These responses were paralleled by increased BAT activity and enhanced response to noradrenaline. Since the DIT with pair-feeding was proportionally as large as with excess intake of the same food in the group fed ad libitum, it is concluded that the palatability of the food, rather than the excess intake per se, is responsible for the increased thermogenesis. DIT was observed when palatable food was fed either ad libitum or in restricted amounts. It is suggested that the palatability of the diet rather than the quantity or composition of the ingested food is responsible for the DIT. It is also proposed that the excess energy expenditure due to sensory stimulation induced by palatable food, is directly related to an enhanced sympathetic activity which stimulates the BAT thermogenic capacity.
Article
To evaluate energy expenditure after three isoenergetic meals of different nutrient composition and to establish the relationship between the thermic effect of food (TEF), subsequent energy intake from a test meal and satiety sensations related to consumption. The study employed a repeated measures design. Ten subjects received, in a randomized order, three meals of 2331+/-36 kJ (557+/-9 kcal). About 68% of energy from protein in the high protein meal (HP), 69% from carbohydrate in the high carbohydrate meal (HC) and 70% from fat in the high fat meal (HF). The experiments were performed at the University of Milan. Subjects: Ten normal body-weight healthy women. Energy expenditure was measured by indirect calorimetric measurements, using an open-circuit ventilated-hood system; intake was assessed 7h later by weighing the food consumed from a test meal and satiety sensations were rated by means of a satiety rating questionnaire. TEF was 261+/-59, 92+/-67 and 97+/-71 kJ over 7 h after the HP, HC and HF meals, respectively. The HP meal was the most thermogenic (P < 0.001) and it determined the highest sensation of fullness (P=0.002). There were no differences in the sensations and thermic effect between fat and carbohydrate meals. A significant relationship linked TEF to fullness sensation (r=0.41, P=0.025). Energy intake from the test meal was comparable after HP, HC and HF meals. Our results suggest that TEF contributes to the satiating power of foods.
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This study investigated the relative satiating hierarchy of the four energy-providing macronutrients (fat, carbohydrate (CHO), protein, and alcohol) in lean women. On four separate occasions, the composition of an iso-energetic lunch preload was manipulated in 12 lean (BMI < 25 kg/m2) women. The four treatments comprised a 1-MJ baseline meal and drink (40% fat, 48% CHO, 12% protein) to which was covertly added: 1) + 1MJ protein; 2) + 1MJ alcohol; 3) + 1MJ CHO; and 4) + 1MJ fat. Prior to and at 30-min intervals, subjects completed 100-mm visual analogue scales rating subjective hunger and satiety. Ninety min following the preload, an ad lib. lunch meal was given (40% fat, 48% CHO, and 12% protein) and energy intake (EI) measured. Energy intake at the lunch meal was 2195 (880, SD) kJ, 2772 (1191, SD) kJ, 2502 (681, SD), kJ and 2558 (1050, SD) kJ for the protein, alcohol, CHO, and fat preloads, respectively. There was no significant difference between the pleasantness of the preloads (p > 0.05). Macronutrient composition had a significant effect on short-term hunger (F = 3.19; p < 0.05), subjects being less hungry after the protein preload. Subjects also had a lower energy intake after the protein preload (F = 3.11; p < 0.05). We conclude that only protein has a differential short-term satiating effect when incorporated iso-energetically and at a similar energy density into the diet.
Article
To investigate the adaptation in substrate utilization to a sudden change in dietary composition from a medium fat to a high fat diet, during a three day period in formerly obese and never obese women. Energy expenditure (EE) and substrate oxidation rates were measured in eight healthy formerly obese women and eight never obese controls, during four consecutive days in a respiration chamber. The first day and the day prior to the experiment, the subjects consumed a diet with 30 energy-% fat, whereas the diet had 55 energy-% fat on the subsequent three days. The rate of adjustment of oxidative substrate partitioning expressed as 24 h non-protein respiratory quotient (RQnp) was similar in the two groups. RQnp on each of the days was also similar between the two groups, after accounting for a group difference in energy balance, caused by a non-significantly lower EE in the formerly obese women. However, the formerly obese subjects, demonstrated a greater suppression of postprandial fat oxidation after supper, which was unrelated to energy balance. Furthermore, the formerly obese subjects, in contrast to the controls, exhibited a reduction in plasma triiodothyronine/thyroxine ratio (T3/T4) following the high fat diet. A positive correlation between T3/T4 and EE was found in the 16 subjects. The formerly obese subjects did not show a slower adaptation rate of substrate utilization when challenged with a high fat diet, but exhibited an enhanced suppression of fat oxidation and a lower T3/T4 ratio after supper, when fed a high fat diet.
Article
The amount and composition of food eaten influence body weight regulation, which requires that, in the long term, energy intake matches energy expenditure and that the oxidation rate to be equal to intake for each and separate nutrients. The aim of this study was to examine the influence of two liquid formulas with different macronutrient composition, a high carbohydrate (HC) meal as compared to a high fat (HF) meal, on substrate oxidation and on thermic effect of food (TEF). Eighteen lean and healthy women which were fed a HC diet during the 3 preceding d were studied for a further 4 h after meal intake. The test meals provided fixed energy intake and whose calculated FQ were 0.77 for HF meal, and 0.96 for HC meal. The mean NPRQs were higher (P < 0.01) in the HC group than in the HF group, even with values greater than 1.00 indicating net lipid synthesis (NL), and which correlated with metabolic rate (MR) value (P < 0.05), glucose (P < 0.05), and heart rate (HR) values. Carbohydrate (CHO) oxidation was higher with the HC than with HF meal (P < 0.01) and correlated with the MR (P < 0.05). Protein oxidation rate rose above baseline (P < 0.01); this increase was accompanied by with a negative CHO balance. It is concluded that the change in fuel selection and the increase of TEF is mainly due to CHO intake and metabolism, respectively, and that surplus of dietary CHO of preceding days together with a large load of CHO can exceed the glycogen storage capacity and trigger NL.
Article
We investigated the effects of food palatability on the thermic effect of feeding (TEF), substrate oxidation and circulating glucose and insulin. Healthy young men (23.4+/-1.0, SD, years, n=10) and older men (69.4+/-1.3, years, n=9) were resident in a metabolic unit for two 2-day study periods. On the second day of each period, they consumed in random order either a palatable test meal containing 2.93 MJ or a nonpalatable control meal containing the same foods in identical amounts but blended and freeze-dried into biscuit form. TEF and respiratory quotient (RQ) were measured over 6 h and blood samples were taken for measurement of glucose and insulin. Age group had no effect on TEF, RQ or circulating glucose other than to delay the time of peak TEF (P<0.002 for both meals). There was no significant effect of meal type on TEF, but RQ and circulating glucose were higher following consumption of the palatable meal (P<0.001 for both parameters). These results suggest that over 6 h postprandial, consumption of palatable foods does not increase TEF, but is instead associated with increased glycemic response and increased carbohydrate oxidation. These changes, combined with previous work on the glycemic index, predict an accelerated return of hunger and increased energy intake at subsequent meals following consumption of palatable vs. control foods. Further studies are needed to examine the possible mechanism for this previously suggested "second meal" effect of diet palatability on energy intake.
Article
It has been suggested that hunger may be delayed and food intake reduced under metabolic conditions that spare carbohydrate oxidation. Our objective was to examine the role of glucose metabolism in the control of food intake in men by using medium-chain triacylglycerols (MCTs) to spare carbohydrate oxidation. In 10 male volunteers, isolated and deprived of any time cues, we studied the effects of 4 lunches on hunger ratings, the duration of satiety, the amount of food ingested at dinner, energy expenditure, substrate oxidation, and plasma variables until the time of the dinner request. One lunch was a basic 2310-kJ meal containing 40 kJ fat substitute (Sub lunch). The 3 other lunches consisted of the same basic meal supplemented with either 1200 kJ long-chain triacylglycerols (LCT lunch), 1200 kJ MCTs (MCT lunch), or 900 kJ carbohydrate plus 300 kJ LCTs (Cho lunch). Energy expenditure was not significantly different after the different lunches, but carbohydrate oxidation was lower after the MCT and LCT lunches than after the Cho lunch. Fat oxidation was greater after the MCT and LCT lunches. The time of the dinner request was significantly delayed after the Cho lunch. Food intake at dinner was significantly lower after the MCT lunch than after the Sub and Cho lunches, but the dinner meal request was not delayed. Carbohydrate may have a greater role in the duration of satiety than does fat, but MCTs may play an active role in other aspects of the control of food intake, especially in satiation at the next meal.
Article
Different dietary fats are metabolized differently in humans and may influence energy expenditure, substrate oxidation, appetite regulation, and body weight regulation. We examined the short-term effects of 4 triacylglycerols (test fats) on subjective appetite, ad libitum energy intake, meal-induced thermogenesis, and postprandial substrate oxidation. Eleven healthy, normal-weight men (mean age: 25.1 +/- 0.5 y) consumed 4 different test fats [conventional fat (rapeseed oil) and 3 modified fats (lipase-structured fat, chemically structured fat, and physically mixed fat)] in a randomized, double-blind, crossover design. No significant differences in appetite sensations or ad libitum energy intakes were observed between the 4 test fats. Overall, the 4 fats exerted different effects on energy expenditure (meal effect: P < 0.01) and substrate oxidation (interaction between meal and time: P < 0.05). In post hoc tests, the 3 modified fats resulted in significantly higher postprandial energy expenditure and fat oxidation than did the conventional fat (P < 0.008, Bonferroni adjusted); no significant differences were observed between the 3 modified fats. Structured fats do not change short-term postprandial appetite sensations or ad libitum energy intakes but do result in higher postprandial energy expenditure and fat oxidation than do conventional fats and hence promote negative energy and fat balance. In humans, a physically mixed fat (trioctanoate + rapeseed oil) is metabolized as quickly as are structured fats. The position of medium-chain fatty acids on the glycerol backbone of triacylglycerols does not seem to affect energy expenditure or appetite.
Article
This study assessed the effects of orosensory stimulation by equipalatable stimuli that differed in macronutrient content (lipid and carbohydrate) on postprandial thermogenesis. Sixteen healthy, normal-weight adults (eight males, eight females) participated in six test sessions conducted weekly. The test sessions were administered randomly after overnight fasts and included: ingestion of 50 g of butter in capsules (to avoid oral stimulation with lipids) and 500 ml of water in 15 min followed by no oral stimulation or oral stimulation with a cracker or one of the following foods on a cracker-butter, unsaturated fatty acid (UFA) margarine, jelly, UFA margarine+jelly. Sensory stimulation entailed masticating and expectorating approximately 5.0 g samples of each stimulus every 3 min for 110 min. Blood was drawn immediately after preload ingestion and at minutes 35, 85, 200, 320, and 440 postloading and was analyzed for insulin, glucagon, and glucose. No significant treatment differences were observed for thermogenesis or oxidation of carbohydrate or lipid. Insulin, glucagon, and glucose concentrations were not different between treatments. These data suggest that orosensory stimulation with stimuli differing in lipid and carbohydrate content, but rated similarly in palatability, does not elicit an increased or differential diet-induced thermogenic response.
Article
The effects of carbohydrate and fat on satiety have been examined primarily through meal composition studies. The purpose of this study was to compare the effects of pure sucrose and safflower oil, isovolumetric beverage preloads, on appetite (measured every 15 minutes by visual analogue scales) and food intake 60 minutes later. Young men consumed 0, 418, 836 and 1254 kJ of sucrose in the first two experiments and these same doses of safflower oil in the third. Finally, the largest doses of sucrose and safflower oil were compared. Sucrose, but not safflower oil, suppressed average appetite compared with control. In experiment 2, food intake was reduced (p<0.05) by 518 kJ after the 418 and 836 kJ preloads and by 1129 kJ after the 1254 kJ sucrose preload. Only the 1254 kJ dose of safflower oil significantly suppressed food intake by 480 kJ in the third experiment. When the 1254 kJ doses were compared directly, sucrose suppressed food intake by 653 kJ compared with control where as safflower oil did not. It is concluded that, in the short-term, sucrose produces a dose dependent reduction in appetite and food intake that is greater than that produced by safflower oil.
Article
Cognitive restraint exerts a limiting effect on food intake in lean individuals. Satiation is the process that determines meal size. Oral, gastric, intestinal, and postabsorptive signals might influence this process. I evaluated the roles of oral and gastric signals in determining meal size in lean women. Nine women ate cereal when they felt hungry under baseline and three treatment conditions: 1) eating until the pleasantness of the flavor of the cereal subsided, 2) eating until the stomach felt full, and 3) eating while watching television. The study was done in a normal living environment. The amounts of cereal consumed under the four conditions were measured. Cereal consumption was similar to that of baseline when the volunteers relied on oral signals to terminate the act of eating. Cereal consumption was significantly higher than baseline when the volunteers ate until they felt full in the stomach and while watching television (P < 0.0001). Recognition of oronasal sensory cues while eating could be the mechanism used by some lean women to limit meal size, and this effect can be offset by cognitive distraction.
Article
Pre-loads high in protein, as compared to carbohydrate and fat, produce greater satiety and reduce food intake after a fixed time interval. This study investigated the effect of macronutrient composition on spontaneous eating behaviour. On four separate occasions, 16 fasted, healthy, non-obese men, blinded to the true purpose of the study, consumed iso-energetic ( approximately 3MJ) yoghurt-based pre-loads of equivalent weight ( approximately 0.5 kg), high in fat (40%) [HF], carbohydrate (60%) [HC] or protein (29%) [HP], and no pre-load in a randomized, single-blind fashion. Subjects ate at will from a selection of food items for the remainder of the day (7 h) with the time of food requests (h) and energy content (kJ) and macronutrient distribution (%) of food eaten recorded. The three pre-loads delayed the first spontaneous request for food by 1.5-1.8 h relative to no pre-load. Total spontaneous food intake was suppressed 29% [HP], 20% [HF] and 17% [HC] by the pre-loads. Neither the amount of food eaten per spontaneous eating episode, nor the spontaneous eating frequency differed statistically following ingestion of the different pre-loads or no pre-load. In this study, in subjects who were free to choose when as well as how much they ate, a high-protein pre-load exerted similar effects on satiety as did iso-energetic high-fat and high-carbohydrate pre-loads.
Article
The maintenance of a stable body weight and composition over time depends, amongst other factors, on the equilibrium in the balance between the intake and metabolic utilisation of the macronutrients in the diet. The organism appears to give greater priority to the adjustment of the oxidation of glucose and amino acids in relation to their ingestion than to the maintenance of the balance of fats. The system of homeostatic self-regulation of the lipid balance is not very efficient, besides which the capacity of storing of energy reserves in the adipose tissue is almost unlimited. Besides, fat appears to confer palatability and flavour on foodstuffs, which could lead to greater consumption. Excessive ingestion of fat is one of the factors that is most frequently associated with a high prevalence of obesity. Some studies indicate that some obese subjects show a reduced capacity for oxidising fatty acids. In this context, the reduction of lipid ingestion is one of the strategies most frequently recommended in the prevention of the epidemic of obesity. However, the role of the lipid intake of the diet in the prevalence and subsequent treatment of obesity is nowadays the subject of scientific controversy.
Article
We investigated the effect of hypocaloric mixed diets with different proportions of carbohydrate, protein, and fat on resting metabolic rate and the thermic effect of food in obese women. Three mixed hypocaloric diets were consumed in random order during separate periods lasting 7 d each. Between each dietary period there was a washout period of 10 d. Diet 1 had a higher proportion of energy from carbohydrate (72%), diet 2 had a higher proportion of energy from protein (43%), and diet 3 had a higher proportion of energy from fat (68%). Indirect calorimetry and lung function tests were done after the completion of each 7-d diet. Seven obese women, ages 22 to 45 y and with body mass indexes of 32 to 59 kg/m(2), participated in the study. Oxygen consumption, carbon dioxide production, resting metabolic rate, and the thermic effect of food by indirect calorimetry were measured. Lung function tests included spirometry in the seated and upright positions, arterial blood gas analysis, and maximal inspiratory and expiratory pressures. There were no statistically significant differences in the resting metabolic rate and the thermic effect of food resulting from the three diets. The mean resting metabolic rates (kJ/d) were 7453 +/- 1446 for diet 1, 7461 +/- 1965 for diet 2, and 7076 +/- 2048 for diet 3. The mean thermic effects of food (kcal/min) were -0.02 +/- 0.07 for diet 1, -0.01 +/- 0.25 for diet 2, and 0.05 +/- 0.13 for diet 3. Lung function tests were normal before and after the hypocaloic diets: partial pressure of oxygen (mmHg) values were 81 +/- 13, 77 +/- 8, and 78 +/- 11 for diets 1 to 3, respectively; and partial pressure of carbon dioxide (mmHg) were 37 +/- 4, 37 +/- 3, and 37 +/- 4 for diets 1 to 3, respectively. Obese women with normal lung function tests and consuming mixed hypocaloric diets showed no alteration in resting metabolic rate and a reduced or absent thermic effect of food independently of the macronutrient composition.
Article
This article has no abstract; the first 100 words appear below. THE regulation of energy intake is fundamental to all homeostatic mechanisms. Yet this basic process has received less attention than many of the physiologic regulations that it makes possible. Before this century, three theories were advanced to account for the phenomenon of hunger. The theories of peripheral origin (Haller, Erasmus Darwin, Johannes Müller and Weber) held that the taking of food resulted from the stimulation either of all afferent nerves by some change in the tissues or of a strictly local group of sensory nerves, mainly in the stomach. The theory of central origin (Magendie, Tidewald and Milne-Edwards) postulated that . . . *From the Department of Nutrition, Harvard School of Public Health. Supported in part by grants-in-aid from the National Institute of Arthritis and Metabolism and the National Heart Institute, National Institutes of Health, Public Health Service, Nutrition Foundation, Incorporated, New York City, Chemistry Scholarship Fund, New York City, National Biscuit Company, New York City, McCallum Foundation, Incorporated, New Brunswick, New Jersey, and Swift and Company, Chicago. Source Information BOSTON † Assistant professor of nutrition, Harvard School of Public Health.
Article
Food ingestion can influence autonomic nervous system activity. This study compares the effects of 2 different isoenergetic meals on sympathetic nervous system (SNS) activity, assessed by heart rate variability (HRV) and plasma norepinephrine (NE) levels, in lean and obese women. Fifteen lean and 15 obese healthy women were examined on 2 occasions: after a carbohydrate (CHO)-rich and after a fat-rich test meal. Measurements of blood pressure, heart rate, resting energy expenditure, plasma glucose, lipids, insulin, leptin, and NE, as well as spectral analysis of the HRV, were performed at baseline and every 1 hour for 3 hours after meals. At baseline, obese women had higher SNS activity than lean controls (higher values of low-to-high frequency ratio [LF/HF], 1.52 +/- 0.31 v 0.78 +/- 0.13, P=.04; and plasma NE levels, 405.6 +/- 197.9 v 240.5 +/- 95.8 pg/mL, P<.0001). After the CHO-rich meal a greater increase in LF/HF and in plasma NE levels was observed in lean, compared to obese women (1.21 +/- 0.6 v 0.32 +/- 0.06, P=.04; and 102.9 +/- 35.4 v 38.7 +/- 12.3 pg/mL, P=.01, respectively), while no differences were observed after the fat-rich meal. Meal-induced thermogenesis was higher after the CHO-rich as compared to the fat-rich meal and was comparable between lean and obese women. Changes in HRV were not associated with the thermogenic response to the test meals. In conclusion, consumption of a CHO-rich meal causes greater cardiac SNS activation in lean than in obese women, while fat ingestion does not result in any appreciable change in either group. SNS activation does not appear to influence the thermic effect of the food in either lean or obese women.
Article
The effect of pure carbohydrate, protein and fat ingestion on different aspects of short-term satiety and their relation to metabolic and cognitive performance indices were studied in 15 healthy male students. Subjects were tested in three sessions for short-term changes in blood indices, indirect calorimetry, different aspects of hunger sensations as well as mood and objective cognitive performance using a repeated-measures, counterbalanced cross-over design. Measurements were made after an overnight fast before and hourly during 3 h after macronutrient ingestion. Preloads were isoenergetic (1670 kJ) spoonable creams with similar sensory properties of either pure carbohydrates, protein or fat. Overall 'desire to eat' and 'gastric emptiness' represented principal components for overall 'hunger' ratings, which were larger after fat and carbohydrate compared with protein ingestion. In the first hour, the hunger suppression of carbohydrates was similar to that of protein and related to changes in beta-hydroxybutyrate and insulin concentrations accompanied with a preference for carbohydrate-rich food. In the third hour, it was similar to the low satiating power of fat and related to diet-induced thermogenesis together with a preference for protein-rich food. For all macronutrients feelings of 'energy' were negatively related to hunger sensations, whereas objective cognitive performance was positively related. Our findings suggest that the subjective satiating effect of carbohydrates seems to change with time in relation to postprandial metabolic changes, presumably mainly dependent on the glycemic response and diet-induced thermogenesis.
Article
The influence of protein and amino acid on the control of food intake and the specific control of protein and amino acid intakes remains incompletely understood. The most commonly accepted conclusions are: (1) the existence of an aversive response to diets deficient in or devoid of protein or deficient in at least one essential amino acid; (2) the existence of a mechanism that enables attainment of the minimum requirement for N and essential amino acids by increasing intake of a low-protein diet; (3) a decrease in the intake of a high-protein diet is associated with different processes, including the high satiating effect of protein. Ingested proteins are believed to generate pre- and post-absorptive signals that contribute to the control of gastric kinetics, pancreatic secretion and food intake. At the brain level, two major afferent pathways are involved in protein and amino acid monitoring: the indirect neuro-mediated (mainly vagus-mediated) pathway and the direct blood pathway. The neuro-mediated pathway transfers pre-absorptive and visceral information. This information is for the main part transferred through the vagus nerve that innervates part of the oro-sensory zone: the stomach, the duodenum and the liver. Other information is directly monitored in the blood. It is likely that the system responds precisely when protein and essential amino acid intake is inadequate, but in contrast allows a large range of adaptive capacities through amino acid degradation and substrate interconversion.
Article
We have recently reported that obese women randomized to a low-carbohydrate diet lost more than twice as much weight as those following a low-fat diet over 6 months. The difference in weight loss was not explained by differences in energy intake because women on the two diets reported similar daily energy consumption. We hypothesized that chronic ingestion of a low-carbohydrate diet increases energy expenditure relative to a low-fat diet and that this accounts for the differential weight loss. To study this question, 50 healthy, moderately obese (body mass index, 33.2 +/- 0.28 kg/m(2)) women were randomized to 4 months of an ad libitum low-carbohydrate diet or an energy-restricted, low-fat diet. Resting energy expenditure (REE) was measured by indirect calorimetry at baseline, 2 months, and 4 months. Physical activity was estimated by pedometers. The thermic effect of food (TEF) in response to low-fat and low-carbohydrate breakfasts was assessed over 5 h in a subset of subjects. Forty women completed the trial. The low-carbohydrate group lost more weight (9.79 +/- 0.71 vs. 6.14 +/- 0.91 kg; P < 0.05) and more body fat (6.20 +/- 0.67 vs. 3.23 +/- 0.67 kg; P < 0.05) than the low-fat group. There were no differences in energy intake between the diet groups as reported on 3-d food records at the conclusion of the study (1422 +/- 73 vs. 1530 +/- 102 kcal; 5954 +/- 306 vs. 6406 +/- 427 kJ). Mean REE in the two groups was comparable at baseline, decreased with weight loss, and did not differ at 2 or 4 months. The low-fat meal caused a greater 5-h increase in TEF than did the low-carbohydrate meal (53 +/- 9 vs. 31 +/- 5 kcal; 222 +/- 38 vs. 130 +/- 21 kJ; P = 0.017). Estimates of physical activity were stable in the dieters during the study and did not differ between groups. These results confirm that short-term weight loss is greater in obese women on a low-carbohydrate diet than in those on a low-fat diet even when reported food intake is similar. The differential weight loss is not explained by differences in REE, TEF, or physical activity and likely reflects underreporting of food consumption by the low-fat dieters.
Article
Manipulations of test meal palatability and nutritional need-state to examine feeding behaviour have, to date, been studied in isolation. Recent investigations have attempted to examine these influences in combination. In the present study, healthy young males received intragastric infusions of soup (265 or 1514 kJ) on four different occasions. The infusion was shortly followed by a meal varying in its palatability (PALATABLE or BLAND). The effect of macronutrient type (CHO or Fat) in the high-energy preloads was also examined in a between-subject manner. High CHO preloads significantly decreased test meal intake and this decrease was unaffected by meal palatability. High fat preloads did not significantly reduce test meal intake. Additionally, more food was consumed following high fat preloads when the test meal was PALATABLE. Within-meal ratings of appetite revealed that hunger was diminished to a greater extent by CHO than by Fat preloads. Appetite was stimulated by the PALATABLE meal to a greater extent in the group receiving Fat than in those receiving the CHO preload. Comparison with a similar oral preloading study revealed differences that suggest possible interactions between cognitive, oro-sensory and gastric controls of feeding when palatable foods are consumed.
Article
When rats experience an unexpected decrease in reward value, e.g., from 32% sucrose to 4% sucrose, consummatory behavior abruptly decreases to a level below control subjects that only experience the lesser reward, a phenomenon known as Successive Negative Contrast (SNC). In food deprived rats experiencing downshifts in sucrose concentration, SNC dissipates in 3-4 days, as consummatory behavior in shifted rats recovers to the level of unshifted controls. In Experiment 1 food deprived rats that were given 5 min daily access to a 2% glucose-0.15% saccharin mixture, and subsequently shifted to 2% glucose alone, displayed a dramatic SNC effect relative to rats that only received 2% glucose. This SNC effect was primarily manifested as a decrease in the number of consummatory bursts initiated. Interestingly, intake failed to recover to control levels during eight daily postshift sessions. However, in Experiment 2 subjects that were shifted from the same glucose-saccharin mixture to 0.15% saccharin alone failed to show SNC rather, intake fell to the level of control animals which only received 0.15% saccharin. The data from Experiment 1, in conjunction with previous studies utilizing non-deprived rats, quinine adulteration, or shifts from sucrose to saccharin, show that reductions in taste value can produce contrast effects, but suggest that a threshold caloric value is necessary for recovery. The data from Experiment 2 may suggest that saccharin and glucose do not contribute equally to the enhanced palatability of the mixture.
Article
Obesity and type 2 diabetes have been associated with a high-fat diet (HFD) and reduced mitochondrial mass and function. We hypothesized a HFD may affect expression of genes involved in mitochondrial function and biogenesis. To test this hypothesis, we fed 10 insulin-sensitive males an isoenergetic HFD for 3 days with muscle biopsies before and after intervention. Oligonucleotide microarray analysis revealed 297 genes were differentially regulated by the HFD (Bonferonni adjusted P < 0.001). Six genes involved in oxidative phosphorylation (OXPHOS) decreased. Four were members of mitochondrial complex I: NDUFB3, NDUFB5, NDUFS1, and NDUFV1; one was SDHB in complex II and a mitochondrial carrier protein SLC25A12. Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC1) alpha and PGC1beta mRNA were decreased by -20%, P < 0.01, and -25%, P < 0.01, respectively. In a separate experiment, we fed C57Bl/6J mice a HFD for 3 weeks and found that the same OXPHOS and PGC1 mRNAs were downregulated by approximately 90%, cytochrome C and PGC1alpha protein by approximately 40%. Combined, these results suggest a mechanism whereby HFD downregulates genes necessary for OXPHOS and mitochondrial biogenesis. These changes mimic those observed in diabetes and insulin resistance and, if sustained, may result in mitochondrial dysfunction in the prediabetic/insulin-resistant state.