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Long-term effects of a very low carbohydrate weight loss diet and an isocaloric low-fat diet on bone health in obese adults
Abstract
Objective:
Compromised bone health is a frequently cited concern of very-low-carbohydrate (LC) diets, although limited data are available from long-term, well-controlled, randomized studies. This study compared the effects of an energy-restricted LC diet and traditional, higher-carbohydrate, low-fat (LF) diet on bone health after 12 mo.
Methods:
One hundred eighteen abdominally obese adults were randomized to consume either an energy-restricted (∼6-7 MJ/d [∼1450-1650 kcal/d]), planned isocaloric LC, or LF diet for 12 mo. Body weight, total body bone mineral content and bone mineral density (BMD), and serum bone crosslaps were assessed pre- and postintervention.
Results:
Sixty-five participants completed the study (LC = 32, LF = 33; age: 51.3 ± 7.1 y; BMI: 33.4 ± 4.0 kg/m(2)). Weight loss was similar in both groups (LC: -14.5 ± 9.8 kg, LF: -11.7 ± 7.3 kg; P = 0.26). By 1 y, total body bone mineral content had not changed in either group (LC: 2.84 ± 0.47 to 2.88 ± 0.49 kg, LF: 3.00 ± 0.52 to 3.00 ± 0.51 kg; P = 0.07 time × diet effect). In both groups, total body BMD decreased (LC: 1.26 ± 0.10 to 1.22 ± 0.09 g/cm(2), LF: 1.26 ± 0.09 to 1.23 ± 0.08 g/m(2); P < 0.001 time) and bone serum crosslaps increased (LC: 319.3 ± 142.6 to 396.5 ± 172.0 ng/L, LF: 276.3 ± 100.6 to 365.9 ± 154.2 ng/L; P < 0.001 time) independent of diet composition (P ≥ 0.25 time × diet effect). Future studies would be strengthened by the assessment of regional BMD at clinically relevant sites (i.e., hip and spine) and multiple markers of bone turnover.
Conclusions:
Weight loss following a hypocaloric LC diet compared with an LF diet does not differentially affect markers of bone health over 12 mo in overweight and obese adults.
... However, in line with our findings, several clinical trial studies demonstrated such null findings. For instance, two randomized clinical trial studies by Brinkworth et al., 34 (n ¼ 65 overweight and obese adults; 12 months) and Foster et al., 35 (n ¼ 307 obese adults; 3 months) showed that weight loss following either a low carbohydrate diet or a low-fat diet did not adversely affect site-specific BMD (e.g., hip and lumbar spine) and bone health parameters. Another study by Carter et al., 36 revealed that consumption of low carbohydrate diet did not affect bone formation (bone-specific alkaline phosphatase (BSAP)), bone resorption (urinary N-telopeptide (UNTx)), and overall bone turnover ratio (BSAP/UNTx) after 3 months of intervention. ...
... Previous clinical trial studies considered the effect of either low or high carbohydrate diet on bone health. 34,35 Therefore, they did not assess the effect of carbohydrate intake in isolation and as a single macronutrient. The contribution and effect of nutritional elements may be different in various contexts, such as nutrient, food, and diet. ...
... The contribution and effect of nutritional elements may be different in various contexts, such as nutrient, food, and diet. Moreover, clinical trial studies considered bone marrow density 34,35 and bone-related biomarkers, 36 which might make the results to be less accurate than assessing the risk of fracture due to the following justifications: First, a large overlap exists between BMD values of patients who suffer from osteoporotic fractures and healthy individual. 71 In the study by Wainwright et al., post hoc analysis showed that more than 50% of postmenopausal women who suffered from bone fracture had BMD T scores greater than À2.5. ...
Objective:
Despite growing evidence for the association between other dietary macronutrients and bone health, limited and inconsistent knowledge is available regarding carbohydrate intake. In this systematic review and meta-analysis, we purposed to clarify and synthesize the knowledge about the relation between carbohydrate intake and the risk of fracture.
Study design:
Systematic review and meta-analysis of observational studies.
Methods:
In this study, PubMed and Scopus were used to conduct a comprehensive search for articles published up to September 2018. The screening was done independently by two authors. Pooled effect sizes were calculated using fixed and random effect models for the highest versus lowest intake categories. The dose-response nature of the relationship was also investigated.
Results:
No association was observed between carbohydrate intake and the risk of fracture in high versus low intake meta-analysis (overall relative risk [RR]: 1.24; 95% confidence interval [95% CI]: 0.84-1.84; P = 0.27) with moderate heterogeneity (I2 = 57.7%, P heterogeneity = 0.05). Moreover, there was no relationship between carbohydrate intake and the risk of fracture in both linear (overall RR: 1.00; 95% CI: 0.94-1.05; P = 0.88) (I2 = 68.1%, P heterogeneity = 0.48) and nonlinear (Pnon-linearity = 0.14) models.
Conclusion:
No association was observed between carbohydrate intake and the risk of fracture.
... The delivery of the dietary intervention was achieved in most of the trials through face-to-face individual and/or group assessment and education. Few trials incorporated a follow-up over the phone and/or via email (29,(37)(38)(39)(40)(41). Behavioral therapy and PA were co-interventions in 39 and 36% of the RCTs, respectively, and 8 RCTs had both co-interventions administered concomitantly ( Table 1). ...
... The compliance to the dietary intervention was assessed in about 50% of the trials using a variety of methods, the most common being food records (32,40,43,(48)(49)(50), followed by food frequency questionnaires and dietary recalls (32,35,51), urine urea nitrogen (41,52,53), and educational sessions' attendance (30,32,33,54). The dropout rate was reported in most studies. ...
Background
Scientists have been investigating efficient interventions to prevent and manage obesity. This network meta-analysis (NMA) compared the effect of different diets [moderate macronutrients (MMs), low fat/high carbohydrate (LFHC), high fat/low carbohydrate (HFLC), and usual diet (UD)] on weight, body mass index (BMI), and waist circumference (WC) changes at ≥12 months.
Methods
We searched Medline, Embase, PubMed databases, and the Cochrane Library. We systematically assessed randomized controlled trials (RCTs) evaluating dietary interventions on adults (mean BMI ≥ 25 kg/m ² ) receiving active dietary counseling for ≥12 months. We pooled the data using a random-effect NMA. We assessed the quality of the included RCTs using the Cochrane risk of bias (ROB) tool.
Results
We included 36 trials, 14 of which compared HFLC with MM diets. Compared with UD, all diets were associated with a significant weight loss (WL) at ≥12 months, HFLC [mean difference in kg (95% CI ): −5.5 (−7.6; −3.4)], LFHC [−5.0 (−7.1; −2.9)] and MM [−4.7 (−6.8; −2.7)]. HFLC, compared with MM diet, was associated with a slightly higher WL (of −0.77 kg) and drop in BMI (of −0.36 kg/m ² ), while no significant difference was detected in other dietary comparisons. WC was lower with all diets compared to UD, with no significant difference across specific diets. There was no significant interaction of the results with the pre-specified sub-groups. The ROB was moderate to high, mostly related to unclear allocation concealment, high dropout rate and unclear or lack of blinding of participants, providers, and outcome assessors.
Conclusion
Dietary interventions extending over ≥12 months are superior to UD in inducing weight, BMI and WC loss. HFLC might be associated with a slightly higher WL compared with MM diets.
Systematic Trial Registration
https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=103116 , PROSPERO (CRD42018103116).
... [36][37][38][39][40][41][42][43][44][45][46][47][48][49] Similarly, 100% of patients with diabetes who received medically-tailored nutrition were found to be adequately compliant, and 93% reported dietary satisfaction. [50][51][52] Findings among patients with chronic kidney disease were also similar. [53][54][55][56][57] Clearly, the provision of medically-tailored meals aids in adherence to dietary recommendations, helping patients overcome the barriers they face in adhering to complex dietary recommendations. ...
... Additionally, provision of low carbohydrate and low calorie diets resulted in A1c reductions comparable to many prominent medication therapies, reducing A1c by 0.9-2.6%. [50][51][52]64 Improvements in A1c control impact many health outcomes including reductions in hospitalizations as well as microvascular and macrovascular complications. 65,66 This novel approach to nutrition where healthcare professionals provide meals to patients is promising with documented improvements in A1c and weight control, offering a new mode of treatment to prevent and/or minimize progression and complications of diabetes. ...
Background
Chronic disease prevalence is increasing. Adherence to dietary guidelines is low (<50%) despite positive impacts in disease progression, clinical outcomes, and medical costs. It is important to summarize the impact of providing medically-tailored meals to patients on adherence rates, clinical outcomes, and potential economic outcomes.
Methods
A systematic review was conducted to identify, extract, and appraise food-provision studies from January 1, 2013-May 1, 2018 for heart disease, diabetes (DM), and chronic kidney disease (CKD). The key findings related to adherence and clinical outcomes were compiled. Published literature was utilized to determine the economic impact of key clinical outcomes.
Results
Across diseases, 100 articles (N = 43,175 patients) were included. Dietary adherence was considered “compliant” or ≥ 90% consistently. Significant (p < 0.05) clinical outcomes included 5–10% LDL reduction, 4-11 mmHg SBP reduction, 30% reduction in metabolic syndrome prevalence, 3–5% weight reduction, 56% lower CKD mortality rates, and increased dialysis-free time (2 years:50%, 5 years:25%, calculated cost savings of 80.6–94.3%). Literature review showed these outcomes would result in decreased: cardiovascular (CV) event risk (20–30% reduction: $5–11 billion annually), hospitalization costs ($1–8 billion), and dialysis rates (25–50% reduction: $14–29 billion annually). For heart failure patients, results include: 16% fewer readmissions (saving $234,096 per 100 patients) and a 38-day shorter length of stay (saving $79,425 per hospitalization).
Conclusion
Providing medically-tailored meals significantly increases dietary adherence above 90% and allows patients to realize significantly better chronic disease control. Through this, patients could experience fewer complications (CV events, hospital readmissions and dialysis), resulting in significant annual US healthcare cost reduction of $27–48 billion.
... Interestingly, the adoption of a Mediterranean diet enriched with virgin olive oil for 2 years is able to modulate a P1NP and OC levels, both biomarkers increased significantly, suggesting a protective effect on bone [67]. Moreover, weight-loss has been generally associated with increase in bone formation as well as resorption biomarkers [68,69]. However, very recent data, obtained in a mouse experimental model, evidenced high-carbohydrate high-fat (HCHF) diet caused a significant increase in CTx level [70]. ...
... p < 0.001) [75]. In another study, conducted on 986 women aged 65 (58)(59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)(70)(71)(72) years referred to coronary angiography, the highest CTx quartile was associated with an increased risk of all-cause and cardiovascular mortality [76]. The lowest 25(OH)D quartile was associated with a trend towards increased risk of noncardiovascular mortality in multivariate analysis, while OC quartile 2 and 3 were significantly associated with lower risk of noncardiovascular mortality [76]. ...
The primary prevention of cardiovascular (CV) disease depends on the capacity to identify subjects at higher risk long before the occurrence of CV clinical manifestations. Traditional risk factors do not cover fully prediction of individual risk. Moreover, there is an area of gray for patients at intermediate CV risk, which offers wide margins of improvement. These observations highlight the need for new additive tools for a more accurate risk stratification. An increasing number of candidate biomarkers have been identified to predict CV risk and events, although they generally give only a moderate increase when added to currently available predictive scores. The approach utilizing a relative small number of biomarkers in multiple combinations, but only weakly related to each other or unrelated, thus belonging to independent-pathways, and so able to catch the multidimensional characteristic of atherosclerosis, appears promising. We discuss vitamin D and bone turnover biomarkers, hepatitis C virus, and psycho-emotional factors that may reflect alternative pathways over those generally considered for atherosclerosis (e.g., aspects directly related to inflammation and thrombosis). These new biomarkers could facilitate a more accurate assessment of CV risk stratification if incorporated in the current risk assessment algorithms.
... There is no evidence that protein intake at levels commonly consumed during TCR is harmful to people with mildly or moderately reduced kidney function [30], and plenty of evidence demonstrates its safety. ...
This chapter gives clinicians the tools to use therapeutic carbohydrate restriction as a dietary intervention for type 2 diabetes patients. The chapter is divided into three section, each addressing a different aspect of therapeutic carbohydrate restriction (TCR). Section 1 delves into the background of carbohydrate restriction, nutrition physiology, the three levels of therapeutic carbohydrate restriction physiological, and metabolic rationale for using TCR to treat the symptoms of type 2 diabetes. Section two explains how to start TCR in a patient population. It goes over which patients are good candidates for TCR and which ones should be approached with caution when implementing this dietary change and explains the importance of baseline assessments. Section three spells out how to administer and manage TCR in a clinical setting. It covers behavior change support, patient education on TCR principles, medication adjustments during the early stages of the intervention, and anticipating and treating common side effects.
... Where multiple reports of the same clinical trial occurred only the primary paper was used for analysis (as confirmed with the relevant authors via email). For example, duplicate papers from one trial [78][79][80][81][82][83][84] were represented by two primary papers from Brinkworth and colleagues [83,84]; and another two reports from one trial [85,86] were represented by Shai and colleagues [86]. A final selection of thirteen unique studies made qualitative mention of a gender difference, yet only five of these published quantitative data to support their claim [86][87][88][89][90]. ...
It has been widely demonstrated that there are a broad range of individual responses to all weight management regimens, often masked by reports of the mean. Identifying features of responders and non-responders to weight loss regimens enables a more tailored approach to the provision of weight management advice. Low-carbohydrate diets are currently popular, and anecdote suggests that males are more successful at losing weight using this approach. This is feasible given the physiological and socio-psychological differences between the genders. We analysed the extent and variation in weight change for males and females separately through a systematic search for all low-carbohydrate diet trials published since 1985. Very few studies compared weight loss outcomes by gender and, of those that did, most lacked supporting data. The majority of studies reported no gender difference but when a gender difference was found, males were more frequently reported as losing more weight than females on a low-carbohydrate diet. The lack of gender stratification in weight loss trials is concerning, as there are a range of gender-based factors that affect weight loss outcomes. This study highlights the importance of examining weight change for males and females separately, since as failure to do so may mask any potential differences, which, if detected, could assist with better weight loss outcomes.
... The important diet caloric contribution to obesity is well documented, and various diets have been studied and compared in the context of prevention and treatment of obesity [77][78][79][80][81][82][83]. The research "obesity-diet" mainly focuses on controlling/limiting the caloric intake to manage obesity or reduce the adiposity. ...
Obesity is a health problem with increasing impacts on public health, economy and even
social life. In order to reestablish the energy balance, obesity management focuses mainly on two pillars; exercise and diet. Beyond the contribution to the caloric intake, the diet nutrients and composition govern a variety of properties. This includes the energy balance-independent properties and the indirect metabolic effects. Whereas the energy balance-independent properties are close to “pharmacological” effects and include effects such as antioxidant and anti-inflammatory, the indirect metabolic effects represent the contribution a diet can have on energy metabolism beyond the caloric contribution itself, which include the food intake control and metabolic changes. As an illustration, we also described the metabolic implication and hypothetical pathways of the high-fat diet induced gene Trefoil Factor Family 2. The properties the diet has can have a variety of applications mainly in pharmacology and nutrition and further explore the “pharmacologically” active food towards potential therapeutic applications.
... However, in contrast to animal studies, all these dietary interventions were performed in middle-aged adults and older people. Among these types of interventions, most of the studies found no differences in BMC and BMD as well as in serum bone turnover markers between individuals receiving a HFD and those receiving a standard diet [78,79] or LFD [80]. In contrast, higher BMC and BMD were reported in women consuming a normocaloric LFD (<28%E from fat) respect than those following a standard diet (30%E from fat). ...
Age-related bone disorders such as osteoporosis or osteoarthritis are a major public health problem due to the functional disability for millions of people worldwide. Furthermore, fractures are associated with a higher degree of morbidity and mortality in the long term, which generates greater financial and health costs. As the world population becomes older, the incidence of this type of disease increases and this effect seems notably greater in those countries that present a more westernized lifestyle. Thus, increased efforts are directed toward reducing risks that need to focus not only on the prevention of bone diseases, but also on the treatment of persons already afflicted. Evidence is accumulating that dietary lipids play an important role in bone health which results relevant to develop effective interventions for prevent bone diseases or alterations, especially in the elderly segment of the population. This review focuses on evidence about the effects of dietary lipids on bone health and describes possible mechanisms to explain how lipids act on bone metabolism during aging. Little work, however, has been accomplished in humans, so this is a challenge for future research.
... Pese a que estudios a largo plazo en ratas reportaron una disminución en masa pancreatica y osea 21,22 , estudios en humanos han mostrado resultados contradictorios. Por un lado, un extenso estudio de cohortes retrospectivo en mujeres australianas de entre 50 y 67 años, reportó que la Tabla 3. Efectos adversos de la cetosis nutricional Efectos adversos del corto plazo [14][15][16] Efectos adversos del largo plazo 12 23 ; pero por otro lado recientes publicaciones, incluyendo un ensayo clínico randomizado no han identificado efectos metabólicos deletéreos en DBC con una adherencia mayor a 6 meses [24][25][26] . Un error común es confundir la cetosis nutricional con la cetosis diabética. ...
With low carbohydrate diets glucose becomes unavailable as a source of energy for our body, leading to the production of ketones from fatty acids in the liver. The increase in plasma ketones is known as nutritional ketosis. The available evidence from basic and clinical studies indicates that both low carbohydrate and high fat low carbohydrate diets are effective for weight loss and are better than non-intervention. However, low carbohydrate diet and ketogenic diets induce unique metabolic changes and consistently improve some markers of cardiovascular risk, lowering elevated blood glucose, insulin, triglycerides, ApoB and saturated fat concentrations, reducing small dense LDL particle numbers, glycated hemoglobin levels, blood pressure and body weight while increasing HDL-cholesterol concentrations and reversing non-alcoholic fatty liver disease. Low carbohydrate diets are an efficient strategy for the management of obesity and metabolic syndrome. They may also benefit patients with polycystic ovary syndrome. They must be prescribed by trained professionals to balance the risks and benefits for each individual patient. Future research is required to improve the knowledge about individual responses to dietary interventions, their safety, tolerance, efficacy and long-term effects.
... An optimal weight loss intervention to reduce disease risk in these populations should target central fat depots, which are pathogenic and grow at a higher rate relative to total body fat in people with advanced age [3]. Additionally, interventions should consider age-specific health concerns, such as the preservation of lean mass and improvement of dyslipidemia and dysglycemia to prevent sarcopenia and reduce disease risk, respectively [2,4]. Yet, there is limited evidence that indicates how particular diet interventions affect these age-specific targets among middle-aged to older adults [2,5]. ...
The objective of this study is to determine whether middle-aged adults prescribed a low carbohydrate-high fat (LCHF) or low fat (LF) diet would have greater loss of central fat and to determine whether the insulin resistance (IR) affects intervention response. A total of 50 participants (52.3 ± 10.7 years old; 36.6 ± 7.4 kg/m2 BMI; 82% female) were prescribed either a LCHF diet (n = 32, carbohydrate: protein: fat of 5%:30%:65% without calorie restriction), or LF diet (n = 18, 63%:13–23%: 10–25% with calorie restriction of total energy expenditure—500 kcal) for 15 weeks. Central and regional body composition changes from dual-x-ray absorptiometry and serum measures were compared using paired t-tests and ANCOVA with paired contrasts. IR was defined as homeostatic model assessment (HOMA-IR) > 2.6. Compared to the LF group, the LCHF group lost more android (15.6 ± 11.2% vs. 8.3 ± 8.1%, p < 0.01) and visceral fat (18.5 ± 22.2% vs. 5.1 ± 15.8%, p < 0.05). Those with IR lost more android and visceral fat on the LCHF verses LF group (p < 0.05). Therefore, the clinical prescription to a LCHF diet may be an optimal strategy to reduce disease risk in middle-aged adults, particularly those with IR.
... In obese men, but not women (mean age of 41 years), decreased total body BMD was observed following body weight loss (11-13%) [154]. By contrast, similar total body BMD decreases were reported for men and women (mean age 51-52 years) following 14% body weight loss [155]. Surprisingly, age and menopausal status do not seem to have a clear impact on how body weight loss affects bone. ...
The implications of obesity and weight loss for human bone health are not well understood. Although the bone changes associated with weight loss are similar in humans and rodents, that is not the case for obesity. In humans, obesity is generally associated with increased bone mass, an outcome which is exacerbated by advanced age and menopause. In rodents, by contrast, bone mass decreases in proportion to severity and duration of obesity, and is influenced by sex, age and mechanical load. Despite these discrepancies, rodents are frequently used to model the situation in humans. In this review, we summarise the existing knowledge of the effects of obesity and weight loss on bone mass in humans and rodents, focusing on the translatability of findings from animal models. We then describe how animal models should be used to broaden the understanding of the relationship between obesity, weight loss, and skeletal health in humans. Specifically, we highlight the aspects of study design that should be considered to optimise translatability of the rodent models of obesity and weight loss. Notably, the sex, age, and nutritional status of the animals should ideally match those of interest in humans. With these caveats in mind, and depending on the research question asked, our review underscores that animal models can provide valuable information for obesity and weight-management research.
... Another frequent concern cited regarding the utilization of a LC diet is its long-term effect on bone health. It was not originally identified by Brinkworth, et al. (2016) suggest there could be a potential association between the increased presence of sulphuric acid from a greater intake of sulphur-containing amino acids attained from higher intakes of protein, which is seen in a LC diet resulting in an adverse effect on bone health. In this study both a LC diet and a LF diet detected small, but significant reductions in BMD (-2.8%). ...
This is the research paper I wrote for the completion of my Master of Science degree in Applied Nutrition. From my perspective, a low-carbohydrate diet can be very beneficial in treating overweight and obesity. It can also be very effective in helping to prevent and manage diabetes. Unfortunately, the terms 'low-carbohydrate' and 'ketogenic" diet often elicit an automatic bias strongly against such programs. Admittedly, I too have a bias in favor of these eating lifestyles. After living a low-carbohydrate lifestyle for more than 2 years and finally achieving success in managing my own type I diabetes after decades of failure, I will continue to promote this lifestyle. This lifestyle has also helped me to lose and maintain 40 pounds (18 kilograms) of body weight.
... The disturbances in bone metabolism caused by a ketogenic diet can be replicated in both mice [21] and rats [22]. It should be noted that the evidence in adults chronically consuming low-carbohydrate, ketogenic diets is sparse with one study suggesting no change in bone biomarkers [23] and others showing disordered calcium metabolism and propensity to renal stone formation [24]. The advantages of dietary choices in treatment of type 2 diabetes, and these low-carbohydrate diets in particular have been discussed in detail, recently [25]. ...
... Studie v trvání 1-2 let, které u obézních jedinců srovnávaly vliv nízkosacharidové a nízkotučné redukční diety na kostní denzitu a markery kost-ního metabolizmu, nezjistily žádný významný rozdíl mezi oběma větvemi a shodně uzavírají, že nízkosacharidová dieta nemá negativní dopad na kostní zdraví. Za potenciálně příznivý vliv LCHF stravy na kostní denzitu lze naopak považovat její vyšší obsah vápníku a vitaminu D [50,51]. ...
There has been an increasing amount of information about the positive results of low-carbohydrate diet in the treatment of diabetes, pre-diabetes, metabolic syndrome and obesity in the form of randomized trials, their meta-analysis and case studies. Many of these indicate that low carbohydrate diets are safe, could significantly improve the compensation of both types of diabetes and the overall health of the diabetic patients. In successful therapy, this diet leads to weight loss, lower medication doses or prescribing, and in some cases of type 2 diabetes also to remission. However, the low carbohydrate diet is not recognized in Czech diabetology, and concerns remain particularly about its safety. This article is a summary of the current knowledge about low-carbohydrate diet, its benefits, risks and contraindications, and aims to initiate a discussion about its use as one of the options for dietary treatment of diabetics. Key words: diabetes mellitus - ketogenic diet - low-carbohydrate diet - metabolic syndrome - obesity.
... However, in the protein and calorie sufficient ketogenic condition, there is no evidence of compromised reproductive ability or appearance of the "female athlete triad", a syndrome of chronic caloric restriction that presents as amenorrhea and osteoporosis. To the contrary, recent studies report that bone density is not adversely affected by a VLC diet (Bertoli et al. (2014), Brinkworth et al. (2016)), and there is preliminary evidence that infertility associated with polycystic ovarian syndrome may be improved by a VLC diet (McGrice and Porter (2017)). Relatedly, while children on ketogenic diets for the treatment of epilepsy do experience reduced growth when protein and calories are restricted, they do not when protein and calories are adequate (Nation et al. (2014)). ...
Obesity is a chronic disease resulting from multifactorial causes mainly related to lifestyle (sedentary lifestyle, inadequate eating habits) and to other conditions such as genetic, hereditary, psychological, cultural, and ethnic factors. The weight loss process is slow and complex, and involves lifestyle changes with an emphasis on nutritional therapy, physical activity practice, psychological interventions, and pharmacological or surgical treatment. Because the management of obesity is a long-term process, it is essential that the nutritional treatment contributes to the maintenance of the individual’s global health. The main diet-related causes associated with excess weight are the high consumption of ultraprocessed foods, which are high in fats, sugars, and have high energy density; increased portion sizes; and low intake of fruits, vegetables, and grains. In addition, some situations negatively interfere with the weight loss process, such as fad diets that involve the belief in superfoods, the use of teas and phytotherapics, or even the avoidance of certain food groups, as has currently been the case for foods that are sources of carbohydrates. Individuals with obesity are often exposed to fad diets and, on a recurring basis, adhere to proposals with promises of quick solutions, which are not supported by the scientific literature. The adoption of a dietary pattern combining foods such as grains, lean meats, low-fat dairy, fruits, and vegetables, associated with an energy deficit, is the nutritional treatment recommended by the main international guidelines. Moreover, an emphasis on behavioral aspects including motivational interviewing and the encouragement for the individual to develop skills will contribute to achieve and maintain a healthy weight. Therefore, this Position Statement was prepared based on the analysis of the main randomized controlled studies and meta-analyses that tested different nutrition interventions for weight loss. Topics in the frontier of knowledge such as gut microbiota, inflammation, and nutritional genomics, as well as the processes involved in weight regain, were included in this document. This Position Statement was prepared by the Nutrition Department of the Brazilian Association for the Study of Obesity and Metabolic Syndrome (ABESO), with the collaboration of dietitians from research and clinical fields with an emphasis on strategies for weight loss.
Purpose of review:
Very low carbohydrate ketogenic diet (KD) therapy has been associated with skeletal demineralization in children with drug-resistant epilepsy, but the cause of this association is unclear. Recently, interest in the KD has grown owing to its potential benefits for other illnesses including cancer, type 2 diabetes, obesity, and polycystic kidney disease. Summaries of the best available evidence regarding effects of a KD on skeletal health are lacking.
Recent findings:
Recent rodent studies found that a KD can harm the growing skeleton, which corroborates most but not all studies in pediatric patients. Proposed mechanisms include chronic metabolic acidosis and depressed osteoanabolic hormones. Relative to other weight-reducing diets, a weight-reducing KD for treatment of obesity and/or type 2 diabetes in adults has not been associated with adverse skeletal effects. By contrast, recent evidence suggests that adaptation to a eucaloric KD may impair bone remodeling in elite adult athletes. Discrepancies in the literature may relate to differences between study populations and in diet formulation.
Summary:
Attention to skeletal health is warranted when using KD therapy given the uncertainty in the literature and suggestive harms in certain populations. Future research should focus on potential mechanisms of injury.
Objective
To carry out a systematic review of published studies to evaluate the relationship between different type of ketogenic diet (KD) and bone health as supported by the scientific literature.
Methods
The study involved all articles that assessed the relationship between the use of KD for the treatment of overweight or obesity and bone health. The quality assessment was evaluated with using the Cambridge Quality Checklists. The search strategy included the following combination of Medical Subjects Headings terms and keywords: “osteoporosis”, ”bone health, ”bone function”, ”bone mineral density”, and “ketogenic diet”.
Results
Seven trials were identified and reviewed. No significant changes in bone mass density (BMD) were observed after KD. The results showed no significant effect on bone resorption by measuring urinary N-telopeptide levels, on bone formation by measuring bone-specific alkaline phosphatase, or alterations in overall bone turnover in patients who followed KD. Only in female subject after a 10% weight loss, bone resorption increases while new bone synthesis decreases, but without increasing the risk of osteoporosis. Finally, patients on KD lost significantly more weight than controls, associated with an increase in serum vitamin D levels and a reduction in plasma parathyroid hormone (PTH) levels.
Conclusion
No human studies have currently been conducted with adequate and powerful experimental designs to definitively understand the impact of KD therapy on bone health.
A plethora of studies to date has examined the roles of feeding-related peptides in the control of food intake. However, the influence of these peptides on the intake of particular macronutrient constituents of food – carbohydrate, fat, and protein – has not been as extensively addressed in the literature. Here, the roles of several feeding-related peptides in controlling macronutrient intake are reviewed. Next, the relationship between macronutrient intake and diseases including diabetes mellitus, obesity, and eating disorders are examined. Finally, some key considerations in macronutrient intake research are discussed. We hope that this review will shed light onto this underappreciated topic in ingestive behavior research and will help to guide further scientific investigation in this area.
Dietary restriction of carbohydrate has been demonstrated to be beneficial for nervous system dysfunction in animal models and may be beneficial for human chronic pain. The purpose of this review is to assess the impact of a low-carbohydrate/ketogenic diet on the adult nervous system function and inflammatory biomarkers to inform nutritional research for chronic pain. An electronic data base search was carried out in May 2021. Publications were screened for prospective research with dietary carbohydrate intake <130g/day and duration of ≥2 weeks. Studies were categorised into those reporting adult neurological outcomes to be extracted for analysis and those reporting other adult research outcomes Both groups were screened again for reported inflammatory biomarkers. From 1548 studies there were 847 studies included. Sixty-four reported neurological outcomes with 83% showing improvement. Five hundred and twenty-three studies had a different research focus (metabolic n=394, sport/performance n=51, cancer n=33, general n=30, neurological with non-neuro outcomes n=12, or gastrointestinal n=4). The second screen identified 63 studies reporting on inflammatory biomarkers with 71% reporting a reduction in inflammation. The overall results suggest a favourable outcome on the nervous system and inflammatory biomarkers from a reduction in dietary carbohydrates. Both nervous system sensitisation and inflammation occur in chronic pain and the results from this review indicate it may be improved by low-carbohydrate nutritional therapy. More clinical trials within this population are required to build on the few human trials that have been done.
A obesidade é um problema de saúde pública mundial que favorece doenças crônicas não transmissíveis afetando a qualidade de vida e o risco de morte. Portanto é necessário combater essa epidemia através da perda de peso corporal. Dietas restritas em carboidrato são alvos de questionamentos sobre eficácia, mecanismo de ação e efeitos adversos. Sob essa definição existe um protocolo dietético que apresenta uma restrição severa em carboidratos, chamada dieta cetogênica que originalmente foi indicada no tratamento não-farmacológico da epilepsia, atualmente tem sido indicada para perda de peso sem ainda haver um consenso na literatura. O objetivo deste trabalho foi realizar uma revisão narrativa da literatura sobre a dieta cetogênica quanto sua eficiência na perda de peso, repercussões metabólicas, performance esportiva e efeitos colaterais. Foram selecionados 27 artigos científicos publicados nos últimos quatorze anos, disponíveis nos portais PubMed, Scielo, Google Acadêmico e BioMed. Em 24 trabalhos houve grupo controle. Em 19 artigos os participantes foram submetidos a protocolos sem restrições calóricas. Em todos os estudos foi constatada a redução de peso ponderal dos participantes. Após a revisão, considera-se que a dieta cetogênica é eficaz na perda de peso, melhora certos parâmetros bioquímicos, porém quando as calorias são controladas os resultados na perda de peso tendem a ser similares a uma dieta controle, embora haja diferenças na bioquímica sérica.
Obesity remains a serious relevant public health concern throughout the world despite related countermeasures being well understood (i.e., mainly physical activity and an adjusted diet). Among different nutritional approaches, there is a growing interest in ketogenic diets (KDs) to manipulate body mass (BM) and to enhance fat mass (FM) loss. KDs reduce the daily amount of carbohydrate intake drastically. This results in increased fatty acid utilization, leading to an increase in blood ketone bodies (KBs) (acetoacetate [AcAc], 3-β-hydroxybutyrate [BHB], and acetone), and therefore metabolic ketosis. For many years, nutritional intervention studies have focused on reducing dietary fat with little or conflicting positive results over the long-term. Moreover, current nutritional guidelines for athletes propose carbohydrate-based diets to augment muscular adaptations. This review discusses the physiological basis of KDs and their effects on BM reduction and body composition improvements in sedentary individuals combined with different types of exercise (resistance training [RT] or endurance training [ET]) in individuals with obesity and athletes. Ultimately, we discuss the strengths and the weaknesses of these nutritional interventions together with precautionary measures that should be observed in both individuals with obesity and athletic populations. A literature search from 1921 to April 2021 using MEDLINE, GOOGLE SCHOLAR, PUBMED, WEB OF SCIENCE, SCOPUS, and SPORTDISCUS databases were used to identify relevant studies. In summary, based on the current evidence, KDs are an efficient method to reduce BM and body fat in both individuals with obesity and athletes. However, these positive impacts are mainly because of the appetite suppressive effects of KDs, which can decrease daily calorie intake. Therefore, KDs do not have any superior benefits to non-KDs in BM and body fat loss in individuals with obesity and athletic populations in an isocaloric situation. In sedentary individuals with obesity, it seems that fat-free mass (FFM) changes appear to be as great, if not greater, than decreases following a low-fat diet (LFD). In terms of lean mass, it seems that following a KD can cause FFM loss in resistance-trained individuals. In contrast, the FFM-preserving effects of KDs are more efficient in endurance-trained compared to resistance-trained individuals.
Background & aims
Nutrition is one of the most important environmental factors affecting the formation of osteopenia. The purpose of this study was to investigate the effects of dietary changes on bone formation and bone resorption markers of postmenopausal women with vertebral osteopenia.
Methods
In this study, 108 women with postmenopausal vertebral osteopenia were included. Patients were observed for a month to identify their regular nutritional status. Before intevention, blood and urine samples were taken from all patients. Then, 2-day food consumption records were taken and the patients were divided into 4 groups. Different types of diets (opposite of their regular diets) were prepared for these groups (1: control, 2: reduced-carbohydrate, 3: reduced-protein, 4: reduced-sodium) and followed for 3 months. At the end of follow-ups, blood and urine samples were taken again and changes in osteocalcin (OC) and N-terminal telopeptide (NTX) levels were examined.
Results
According to biochemical analysis, there was a significant decrease (p<0,001) in OC levels in reduced protein group and an increase (p>0,05) in reduced carbohydrate group. When NTX levels were assessed, a significant decrease (p<0.001) in the reduced carbohydrate group and a significant increase in the reduced protein group (p<0.05) were found.
Conclusion
Our findings show that reduced carbohydrate diet protected whereas, reduced protein diet negatively affected bone health. Osteopenic individuals were thought to be able to improve bone health and their quality of life by early dietary intervention.
A systematic review of published evidence on micronutrient intake/status with carbohydrate‐restricted diets (CRD) was conducted in Web of Science, Medline, Embase, Scopus, CENTRAL, and ClinicalTrials.gov up to October 2018. We identified 10 studies: seven randomized controlled trials (RCTs) (“Atkins”‐style, n = 5; “Paleolithic” diets, n = 2), two Atkins‐style noncontrolled trials and one cross‐sectional study. Prescribed carbohydrate varied 4% to 34% of energy intake. Only one noncontrolled trial prescribed multivitamin supplements. Dietary intakes/status were reported over 2 to 104 weeks, with weight losses from 2 to 9 kg. No diagnoses of deficiency were reported. Intakes of thiamine, folate, magnesium, calcium, iron, and iodine all decreased significantly (−10% to −70% from baseline) with any CRD types. Atkins diet trials (n = 6; 4%‐34%E carbohydrate) showed inconsistent changes in vitamin A, E, and β‐carotene intakes, while a single “Paleolithic” diet trial (28%E carbohydrate) reported increases in these micronutrients. One other “Paleolithic” diet (30%E carbohydrate) reported a rise in moderate iodine deficiency from 15% to 73% after 6 months. In conclusion, few studies have assessed the impacts of CRD on micronutrients. Studies with different designs point towards reductions in several vitamins and minerals, with potential risk of micronutrient inadequacies. Trial reporting standards are expected to include analysis of micronutrient intake/status. Micronutrients in foods and/or supplements should be considered when designing, prescribing or following CRDs.
Background:
The choice of hypocaloric diets in obesity can affect bone health.
Aims:
The aim of this study is to assess the effect of a hypocaloric diet in postmenopausal obese women and to determine the influence of weight reduction on bone metabolism.
Methods:
This was a non-randomised, single-treatment study in 96 postmenopausal women with a body mass index (BMI) greater than 35kg/m2 and osteoarthritis. The patients received a formula diet with two intake levels of a normocaloric hyperproteic formula (1035kcal (25% protein)). Anthropometry and biochemistry with CrossLaps, osteocalcin, parathyroid hormone (PTH) and 25-OH vitamin D were measured. Consumption of protein, calcium and vitamin D were determined at the beginning of and 3 and 6 months into the study. The response to treatment was compared (high-responder (HR): weight loss greater than 15%, and low-responder (LR): weight loss less than 15%).
Results:
The mean age was 64.2 (7.5) years. After 6 months of treatment, a weight loss of 10.2% (8.2-13.8) was observed. There was a significant increase in vitamin D (HR: 21.8% (36.2) vs. LR: 22.7% (36.9), p=0.93) and CrossLaps (HR: 26.8% (19.5-35.2)) vs. LR: 13.3% (-6.1 to 27.9), p=0.01). The loss of more than 15% of initial body weight was an independent risk factor for an increase in CrossLaps (OR: 4.22 (1.1-16.8), p=0.04).
Conclusions:
In postmenopausal obese women, weight loss was associated with an increase in the biochemical parameters of bone resorption. The increase in resorption parameters was related to the magnitude of weight loss.
Introduction: Type 2 diabetes is associated with an increased risk of bone fractures. Bone mineral density (BMD) is increased and bone turnover is low in type 2 diabetes and the increased BMD does not explain the increased fracture risk. However, the low bone turnover may lead to insufficient bone renewal with unrepaired micro-cracks and thus increase fracture risk. Ingestion of food acutely decreases bone resorption markers and the macronutrient composition of meals and meal frequency may influence bone metabolism adversely in subjects with unhealthy eating patterns, e.g. patients with type 2 diabetes.
Areas covered: The treatment strategy of bone disease in type 2 diabetics is covered in this review. The current management of diabetic bone disease consists of anti-osteoporotic treatment. However, anti-resorptives may further reduce an already low bone turnover with uncertain effects. Furthermore, the acute and long-term effects of meal ingestion, weight loss alone and in combination with exercise as well as the possible underlying mechanisms are covered in this systematic review.
Expert Commentary: Current management of diabetic bone disease is based on principles of anti-osteoporotic treatment in non-diabetic subjects. However, studies are urged to investigate whether anti-resorptives are equally beneficial in type 2 diabetes as in non-diabetic individuals.
Objectives:
This report presents bone measurement data from total body dual energy x-ray absorptiometry scans for 28,454 persons aged 8 years and over who participated in the 1999-2006 National Health and Nutrition Examination Survey. The sample consisted of 22,667 respondents with valid data, and 5,787 with missing data that were successfully multiply imputed (i.e., not highly variable). Bone area, bone mineral content, and bone mineral density (BMD) are presented for the total body, the total body minus the head (e.g., subtotal), and 10 subregions of the body.
Methods:
Means, standard deviations, and selected percentiles were calculated for the total body, total body minus head (subtotal), and 10 body subregions by sex, race and ethnicity, and age. Smoothed mean total body BMD was plotted by age, sex, and race and ethnicity. Multiple regression was used to evaluate differences in mean total body BMD by age, sex, and race and ethnicity.
Results:
After adjusting for race and ethnicity, total body BMD among those under age 20 was significantly higher in respondents aged 12-19 than in those aged 8-11 in both sexes. Among adults of both sexes, total body BMD in persons aged 20-49 was significantly higher than in those aged 50-79, and significantly lower in persons aged 80 and over than in those aged 50-79, after adjusting for race and ethnicity. After adjusting for age, total body BMD was significantly higher in non-Hispanic black persons than in non-Hispanic white persons, regardless of age or sex. However, the pattern differed by age when Mexican-American persons were compared with non-Hispanic white persons: Age-adjusted total body BMD was significantly lower among Mexican-American males aged 8-19, was similar in Mexican-American females aged 8-19, and was significantly lower in Mexican-American men and women aged 20 and over.
Previous studies comparing low-carbohydrate and low-fat diets have not included a comprehensive behavioral treatment, resulting in suboptimal weight loss.
To evaluate the effects of 2-year treatment with a low-carbohydrate or low-fat diet, each of which was combined with a comprehensive lifestyle modification program.
Randomized parallel-group trial. (ClinicalTrials.gov registration number: NCT00143936)
3 academic medical centers.
307 participants with a mean age of 45.5 years (SD, 9.7 years) and mean body mass index of 36.1 kg/m(2) (SD, 3.5 kg/m(2)).
A low-carbohydrate diet, which consisted of limited carbohydrate intake (20 g/d for 3 months) in the form of low-glycemic index vegetables with unrestricted consumption of fat and protein. After 3 months, participants in the low-carbohydrate diet group increased their carbohydrate intake (5 g/d per wk) until a stable and desired weight was achieved. A low-fat diet consisted of limited energy intake (1200 to 1800 kcal/d; <or=30% calories from fat). Both diets were combined with comprehensive behavioral treatment.
Weight at 2 years was the primary outcome. Secondary measures included weight at 3, 6, and 12 months and serum lipid concentrations, blood pressure, urinary ketones, symptoms, bone mineral density, and body composition throughout the study.
Weight loss was approximately 11 kg (11%) at 1 year and 7 kg (7%) at 2 years. There were no differences in weight, body composition, or bone mineral density between the groups at any time point. During the first 6 months, the low-carbohydrate diet group had greater reductions in diastolic blood pressure, triglyceride levels, and very-low-density lipoprotein cholesterol levels, lesser reductions in low-density lipoprotein cholesterol levels, and more adverse symptoms than did the low-fat diet group. The low-carbohydrate diet group had greater increases in high-density lipoprotein cholesterol levels at all time points, approximating a 23% increase at 2 years.
Intensive behavioral treatment was provided, patients with dyslipidemia and diabetes were excluded, and attrition at 2 years was high.
Successful weight loss can be achieved with either a low-fat or low-carbohydrate diet when coupled with behavioral treatment. A low-carbohydrate diet is associated with favorable changes in cardiovascular disease risk factors at 2 years.
National Institutes of Health.
There has been a resurgence of interest in the controversial relation between dietary protein and bone health.
This article reports on the first systematic review and meta-analysis of the relation between protein and bone health in healthy human adults.
The MEDLINE (January 1966 to September 2007) and EMBASE (1974 to July 2008) databases were electronically searched for all relevant studies of healthy adults; studies of calcium excretion or calcium balance were excluded.
In cross-sectional surveys, all pooled r values for the relation between protein intake and bone mineral density (BMD) or bone mineral content at the main clinically relevant sites were significant and positive; protein intake explained 1-2% of BMD. A meta-analysis of randomized placebo-controlled trials indicated a significant positive influence of all protein supplementation on lumbar spine BMD but showed no association with relative risk of hip fractures. No significant effects were identified for soy protein or milk basic protein on lumbar spine BMD.
A small positive effect of protein supplementation on lumbar spine BMD in randomized placebo-controlled trials supports the positive association between protein intake and bone health found in cross-sectional surveys. However, these results were not supported by cohort study findings for hip fracture risk. Any effects found were small and had 95% CIs that were close to zero. Therefore, there is a small benefit of protein on bone health, but the benefit may not necessarily translate into reduced fracture risk in the long term.
Long-term weight loss and cardiometabolic effects of a very-low-carbohydrate, high-saturated-fat diet (LC) and a high-carbohydrate, low-fat diet (LF) have not been evaluated under isocaloric conditions.
The objective was to compare an energy-controlled LC diet with an LF diet at 1 y.
Men and women (n = 118) with abdominal obesity and at least one additional metabolic syndrome risk factor were randomly assigned to either an energy-restricted (approximately 6-7 MJ) LC diet (4%, 35%, and 61% of energy as carbohydrate, protein, and fat, respectively) or an isocaloric LF diet (46%, 24%, and 30% of energy as carbohydrate, protein, and fat, respectively) for 1 y. Weight, body composition, and cardiometabolic risk markers were assessed.
Sixty-nine participants (59%) completed the trial: 33 in the LC group and 36 in the LF group. Both groups lost similar amounts of weight (LC: -14.5 +/- 1.7 kg; LF: -11.5 +/- 1.2 kg; P = 0.14, time x diet) and body fat (LC: -11.3 +/- 1.5 kg; LF: -9.4 +/- 1.2 kg; P = 0.30). Blood pressure, fasting glucose, insulin, insulin resistance, and C-reactive protein decreased independently of diet composition. Compared with the LF group, the LC group had greater decreases in triglycerides (-0.36 +/- 0.15 mmol/L; 95% CI: -0.67, -0.05 mmol/L; P = 0.011), increases in HDL cholesterol (0.23 +/- 0.09 mmol/L; 95% CI: 0.06, 0.40 mmol/L; P = 0.018) and LDL cholesterol (0.6 +/- 0.2 mmol/L; 95% CI: 0.2, 1.0 mmol/L; P = 0.001), and a greater but nonsignificant increase in apolipoprotein B (0.08 +/- 0.04 g/L; 95% CI: -0.004, 0.171 g/L; P = 0.17).
Under planned isoenergetic conditions, as expected, both dietary patterns resulted in similar weight loss and changes in body composition. The LC diet may offer clinical benefits to obese persons with insulin resistance. However, the increase in LDL cholesterol with the LC diet suggests that this measure should be monitored. This trial was registered with the Australian New Zealand Clinical Trials Registry at (http://www.anzctr.org.au) as ACTR 12606000203550.
The average American diet, which is high in protein and low in fruits and vegetables, generates a large amount of acid, mainly as sulfates and phosphates. The kidneys respond to this dietary acid challenge with net acid excretion, as well as ammonium and titratable acid excretion. Concurrently, the skeleton supplies buffer by active resorption of bone. Indeed, calciuria is directly related to net acid excretion. Different food proteins differ greatly in their potential acid load, and therefore in their acidogenic effect. A diet high in acid-ash proteins causes excessive calcium loss because of its acidogenic content. The addition of exogenous buffers, as chemical salts or as fruits and vegetables, to a high protein diet results in a less acid urine, a reduction in net acid excretion, reduced ammonium and titratable acid excretion, and decreased calciuria. Bone resorption may be halted, and bone accretion may actually occur. Alkali buffers, whether chemical salts or dietary fruits and vegetables high in potassium, reverse acid-induced obligatory urinary calcium loss. We conclude that excessive dietary protein from foods with high potential renal acid load adversely affects bone, unless buffered by the consumption of alkali-rich foods or supplements.
Weight loss may lead to bone loss but little is known about changes in bone mass during regain of reduced weight. We studied changes in bone mineral density (BMD) and bone mineral content (BMC) during voluntary weight reduction and partial regain. The study consisted of three phases: a 3 month weight reduction with very-low-energy diet (VLED), a 9 month randomized, controlled walking intervention period with two training groups (target energy expenditure 4.2 or 8.4 MJ/week) and a 24-month follow-up. The participants were premenopausal women with a mean body mass index of 34.0 (SD 3.6) kg/m2. Seventy-four of 85 subjects completed the whole study. Total body, lumbar spine, proximal femur and dominant radius BMD and BMC were measured with dual-energy X-ray absorptiometry (DXA). The mean weight loss during VLED was 13.2 (3.4) kg, accompanied by unchanged total body BMC and decreased lumbar, trochanteric and radial BMD (p < 0.05). During months 3-36, an average of 62% of the weight loss was regained, total body BMC decreased and trochanteric BMD increased (p < 0.05). At the end of the study, total body BMC and lumbar and femoral neck BMD were lower than initially (p < 0.05). Weight change throughout the study correlated significantly with the change in radial (r = 0.54), total body (r = 0.39) and trochanteric (r = 0.37) BMD. Exercise-group assignment had no effect on BMD at weight-bearing sites. In conclusion, the observed changes in BMD and BMC during weight reduction and its partial regain were clinically small and partly reversible. More studies are needed to clarify whether the observed weight changes in BMD and BMC are real or are artifacts arising from assumptions, inaccuracies and technical limitations of DXA.
Bone loss often accompanies weight loss induced by caloric restriction (CR), but whether bone loss accompanies similar weight loss induced by exercise (EX) is unknown. We tested the hypothesis that EX-induced weight loss is associated with less bone loss compared with CR-induced weight loss.
Forty-eight adults (30 women; 18 men; mean +/- SD age, 57 +/- 3 years; and mean +/- SD body mass index, 27 +/- 2 kg/m2) were randomized to 1 of 3 groups for 1 year: CR group (n = 19), regular EX group (n = 19), or a healthy lifestyle (HL) control group (n = 10). Primary outcome measure was change in hip and spine bone mineral density (BMD). Secondary outcomes were bone markers and hormones.
Body weight decreased similarly in the CR and EX groups (10.7% +/- 6.3% [-8.2 +/- 4.8 kg] vs 8.4% +/- 6.3% [-6.7 +/- 5.6 kg]; P = .21), whereas weight did not change in the HL group (-1.2% +/- 2.5% [-0.9 +/- 2.0 kg]). Compared with the HL group, the CR group had decreases in BMD at the total hip (-2.2% +/- 3.1% vs 1.2% +/- 2.1%; P = .02) and intertrochanter (-2.1% +/- 3.4% vs 1.7 +/- 2.8%; P = .03). The CR group had a decrease in spine BMD (-2.2% +/- 3.3%; P = .009). Despite weight loss, the EX group did not demonstrate a decrease in BMD at any site. Body weight changes correlated with BMD changes in the CR (R = 0.61; P = .007) but not in the EX group. Bone turnover increased in both CR and EX groups.
CR-induced weight loss, but not EX-induced weight loss, is associated with reductions in BMD at clinically important sites of fracture. These data suggest that EX should be an important component of a weight loss program to offset adverse effects of CR on bone.
Context:
Popular diets, particularly those low in carbohydrates, have challenged current recommendations advising a low-fat, high-carbohydrate diet for weight loss. Potential benefits and risks have not been tested adequately.
Objective:
To compare 4 weight-loss diets representing a spectrum of low to high carbohydrate intake for effects on weight loss and related metabolic variables.
Design, setting, and participants:
Twelve-month randomized trial conducted in the United States from February 2003 to October 2005 among 311 free-living, overweight/obese (body mass index, 27-40) nondiabetic, premenopausal women.
Intervention:
Participants were randomly assigned to follow the Atkins (n = 77), Zone (n = 79), LEARN (n = 79), or Ornish (n = 76) diets and received weekly instruction for 2 months, then an additional 10-month follow-up.
Main outcome measures:
Weight loss at 12 months was the primary outcome. Secondary outcomes included lipid profile (low-density lipoprotein, high-density lipoprotein, and non-high-density lipoprotein cholesterol, and triglyceride levels), percentage of body fat, waist-hip ratio, fasting insulin and glucose levels, and blood pressure. Outcomes were assessed at months 0, 2, 6, and 12. The Tukey studentized range test was used to adjust for multiple testing.
Results:
Weight loss was greater for women in the Atkins diet group compared with the other diet groups at 12 months, and mean 12-month weight loss was significantly different between the Atkins and Zone diets (P<.05). Mean 12-month weight loss was as follows: Atkins, -4.7 kg (95% confidence interval [CI], -6.3 to -3.1 kg), Zone, -1.6 kg (95% CI, -2.8 to -0.4 kg), LEARN, -2.6 kg (-3.8 to -1.3 kg), and Ornish, -2.2 kg (-3.6 to -0.8 kg). Weight loss was not statistically different among the Zone, LEARN, and Ornish groups. At 12 months, secondary outcomes for the Atkins group were comparable with or more favorable than the other diet groups.
Conclusions:
In this study, premenopausal overweight and obese women assigned to follow the Atkins diet, which had the lowest carbohydrate intake, lost more weight at 12 months than women assigned to follow the Zone diet, and had experienced comparable or more favorable metabolic effects than those assigned to the Zone, Ornish, or LEARN diets [corrected] While questions remain about long-term effects and mechanisms, a low-carbohydrate, high-protein, high-fat diet may be considered a feasible alternative recommendation for weight loss.
Trial registration:
clinicaltrials.gov Identifier: NCT00079573.
In brief: Calcium deficiency regularly produces osteoporosis in experimental animals. Adequate calcium intakes are essential for human bone health as well. However, human osteoporosis results from several factors; calcium deficiency is only one, and high calcium intake will prevent only those cases in which calcium is the limiting factor. Calcium, for example, will not reverse the bone loss due to inactivity. Because calcium requirement cannot feasibly be determined individually, it makes good sense to ensure a high calcium intake for every member of the population.
Diet-induced weight loss has been suggested to be harmful to bone health. We conducted a systematic review and meta-analysis (using a random-effects model) to quantify the effect of diet-induced weight loss on bone. We included 41 publications involving overweight or obese but otherwise healthy adults who followed a dietary weight loss intervention. The primary outcomes examined were changes from baseline in total hip, lumbar spine and total body BMD, as assessed by dual energy X-ray absorptiometry. Secondary outcomes were markers of bone turnover. Diet-induced weight loss was associated with significant decreases of 0.010-0.015 g/cm(2) in total hip BMD for interventions of 6, 12 or 24 (but not 3) months' duration ([95% confidence intervals] [-0.014 to -0.005], [-0.021 to -0.008], and [-0.024 to -0.000] g/cm(2) at 6, 12 and 24 months, respectively). There was however no statistically significant effect of diet-induced weight loss on lumbar spine or whole body BMD for interventions of 3 to 24 months' duration, except for a significant decrease in total body BMD (-0.011 [-0.018 to -0.003] g/cm(2) ) after 6 months. While no statistically significant changes occurred in serum concentrations of N-terminal propeptide of type I procollagen (P1NP), interventions of 2 or 3 months in duration (but not of 6, 12 or 24 months' durations) induced significant increases in serum concentrations of osteocalcin (0.26 [0.13-0.39] nmol/L), C-terminal telopeptide of type I collagen (CTX, 4.72 [2.12-7.30] nmol/L) or N-terminal telopeptide of type I collagen (NTX, 3.70 [0.90-6.50] nmol/L bone collagen equivalents [BCE]), indicating an early effect of diet-induced weight loss to promote bone breakdown. These data show that in overweight and obese individuals, a single diet-induced weight loss intervention induces a small decrease in total hip BMD, but not lumbar spine BMD. This decrease is small in comparison to known metabolic benefits of losing excess weight. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Background:
Previous studies comparing low-carbohydrate and low-fat diets have not included a comprehensive behavioral treatment, resulting in suboptimal weight loss.
Objective:
To evaluate the effects of 2-year treatment with a low-carbohydrate or low-fat diet, each of which was combined with a comprehensive lifestyle modification program.
Design:
Randomized parallel-group trial. (ClinicalTrials.gov registration number: NCT00143936)
Setting:
3 academic medical centers.
Patients:
307 participants with a mean age of 45.5 years (SD, 9.7 years) and mean body mass index of 36.1 kg/m(2) (SD, 3.5 kg/m(2)).
Intervention:
A low-carbohydrate diet, which consisted of limited carbohydrate intake (20 g/d for 3 months) in the form of low-glycemic index vegetables with unrestricted consumption of fat and protein. After 3 months, participants in the low-carbohydrate diet group increased their carbohydrate intake (5 g/d per wk) until a stable and desired weight was achieved. A low-fat diet consisted of limited energy intake (1200 to 1800 kcal/d; <or=30% calories from fat). Both diets were combined with comprehensive behavioral treatment.
Measurements:
Weight at 2 years was the primary outcome. Secondary measures included weight at 3, 6, and 12 months and serum lipid concentrations, blood pressure, urinary ketones, symptoms, bone mineral density, and body composition throughout the study.
Results:
Weight loss was approximately 11 kg (11%) at 1 year and 7 kg (7%) at 2 years. There were no differences in weight, body composition, or bone mineral density between the groups at any time point. During the first 6 months, the low-carbohydrate diet group had greater reductions in diastolic blood pressure, triglyceride levels, and very-low-density lipoprotein cholesterol levels, lesser reductions in low-density lipoprotein cholesterol levels, and more adverse symptoms than did the low-fat diet group. The low-carbohydrate diet group had greater increases in high-density lipoprotein cholesterol levels at all time points, approximating a 23% increase at 2 years.
Limitation:
Intensive behavioral treatment was provided, patients with dyslipidemia and diabetes were excluded, and attrition at 2 years was high.
Conclusion:
Successful weight loss can be achieved with either a low-fat or low-carbohydrate diet when coupled with behavioral treatment. A low-carbohydrate diet is associated with favorable changes in cardiovascular disease risk factors at 2 years.
Primary funding source:
National Institutes of Health.
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Studies of body-composition changes during weight loss have had conflicting results with regard to changes in bone mineral content (BMC) and bone mineral density (BMD). We examined BMC and BMD for changes during weight loss. Fourteen women enrolled in a 15-wk weight loss program. Dual-energy X-ray absorptiometry (DXA) measures of the total body were made at baseline (T1), the midpoint of weight loss (T2), and at the end of weight loss (T3). Body weight changed significantly throughout the 15 wk, declining from a high of 89.7+/-3.6 to 74.1+/-3.2 kg. Fat-free mass declined initially (47.8+/-1.7 kg at T1, 45.7+/-1.4 kg at T2, and 46.0+/-1.5 kg at T3) and then stabilized. Fat mass changed significantly during the study (39.2 kg at T1, 32.4 kg at T2, and 29.3 kg at T3). No significant differences were observed in BMC or bone areal measurement during the study. However, BMD declined significantly from baseline (1.217 g/cm2 at T1, 1.197 g/cm2 at T2, and 1.200 g/cm2 at T3). The changes in BMC and BA were in opposite directions, resulting in a significant decline in BMD without a loss of BMC. These data suggest that changes in BMD observed with weight loss may be the result of a lack of instrument sensitivity when body weight and composition change and are simply an artifact and not a physiologic change in BMD. Further research is needed to determine the full effect of weight loss on BMC, bone area, and BMD.
Although calcium and vitamin D have been the primary focus of nutritional prevention of osteoporosis, recent research has clarified the importance of several additional nutrients and food constituents. Further, results of calcium and vitamin D supplementation trials have been inconsistent, suggesting that reliance on this intervention may be inadequate. In addition to dairy, fruit and vegetable intake has emerged as an important modifiable protective factor for bone health. Several nutrients, including magnesium, potassium, vitamin C, vitamin K, several B vitamins, and carotenoids, have been shown to be more important than previously realized. Rather than having a negative effect on bone, protein intake appears to benefit bone status, particularly in older adults. Regular intake of cola beverages shows negative effects and moderate alcohol intake shows positive effects on bone, particularly in older women. Current research on diet and bone status supports encouragement of balanced diets with plenty of fruit and vegetables, adequate dairy and other protein foods, and limitation of foods with low nutrient density.
Age-adjusted female hip fracture incidence has been noted to be higher in industrialized countries than in nonindustrialized countries. A possible explanation that has received little attention is that elevated metabolic acid production associated with a high animal protein diet might lead to chronic bone buffering and bone dissolution. In an attempt to examine this hypothesis, cross-cultural variations in animal protein consumption and hip fracture incidence were examined. When female fracture rates derived from 34 published studies in 16 countries were regressed against estimates of dietary animal protein, a strong, positive association was found. This association could not plausibly be explained by either dietary dietary calcium or total caloric intake. Recent studies suggest that the animal protein-hip fracture association could have a biologically tenable basis. We conclude that further study of the metabolic acid-osteoporosis hypothesis is warranted.
Based on data from 153 early postmenopausal women who completed a double-blind, randomized 3 year study of graded hormone replacement therapy (HRT) doses or placebo, we investigated the value of bone markers to predict prevention of bone loss. Absolute values of serum and urinary CrossLaps (S-CTX and U-CTX) after 2 weeks of treatment were significantly correlated to 3 year bone mass response (r = -0. 28/-0.35; p < 0.001). These associations were fully expressed at 6 months (r = -0.61/-0.64; p < 0.001). Receiver operating characteristic analyses revealed that the predictive capacity of one measurement of a resorption marker after 6 months' treatment performed similarly as assessment of hip bone mass over 3 years in predicting preservation of spinal bone mass over 3 years. Comparable results were obtained using percent change from baseline in resorption markers at both 6 and 12 months, whereas for formation markers percent change was superior to absolute value at 6 months but not at 12 months. Values of accuracy for S-CTX for a cutoff of 1881 pmol/L at 6 months were 85.2% (sensitivity), 74.3% (specificity), 90.5% (positive predictive value), and 63.4% (negative predictive value); U-CTX performed similarly, whereas the values for the formation markers were slightly lower. A cutoff for S-CTX of 1245 pmol/L eliminated false-positive individuals (those who had a decrease below the cutoff but lost bone). In the false-negative group, which was composed of individuals whose S-CTX did not decrease below the cutoff but had preserved bone mass, S-CTX was significantly associated with spinal bone mass response (r = -0. 41; p < 0.01), indicating these women had been treated with a dose that was not at its optimum for their individual bone turnover. For this cutoff, the values were 49.5% (sensitivity), 97.1% (specificity), 98% (positive predictive value), and 40% (negative predictive value). In conclusion, early bone marker measurements predict long-term preservation of bone mass during HRT. Resorption markers seem superior to formation markers, which reflects that the primary effect of HRT is on bone resorption. A strategy with two cutoff levels may optimize the use of bone markers to predict bone mass response. Whether resorption markers can be used to guide individualized treatment remains to be investigated.
Low-carbohydrate high-protein (LCHP) diets are used commonly for weight reduction. This study explores the relationship between such diets and acid-base balance, kidney-stone risk, and calcium and bone metabolism.
Ten healthy subjects participated in a metabolic study. Subjects initially consumed their usual non-weight-reducing diet, then a severely carbohydrate-restricted induction diet for 2 weeks, followed by a moderately carbohydrate-restricted maintenance diet for 4 weeks. Results: Urine pH decreased from 6.09 (Usual) to 5.56 (Induction; P < 0.01) to 5.67 (Maintenance;P < 0.05). Net acid excretion increased by 56 mEq/d (Induction; P < 0.001) and 51 mEq/d (Maintenance; P < 0.001) from a baseline of 61 mEq/d. Urinary citrate levels decreased from 763 mg/d (3.98 mmol/d) to 449 mg/d (2.34 mmol/d; P < 0.01) to 581 mg/d (3.03 mmol/d; P < 0.05). Urinary saturation of undissociated uric acid increased more than twofold. Urinary calcium levels increased from 160 mg/d (3.99 mmol/d) to 258 mg/d (6.44 mmol/d; P < 0.001) to 248 mg/d (6.19 mmol/d; P < 0.01). This increase in urinary calcium levels was not compensated by a commensurate increase in fractional intestinal calcium absorption. Therefore, estimated calcium balance decreased by 130 mg/d (3.24 mmol/d; P < 0.001) and 90 mg/d (2.25 mmol/d; P < 0.05). Urinary deoxypyridinoline and N-telopeptide levels trended upward, whereas serum osteocalcin concentrations decreased significantly (P < 0.01).
Consumption of an LCHP diet for 6 weeks delivers a marked acid load to the kidney, increases the risk for stone formation, decreases estimated calcium balance, and may increase the risk for bone loss.
Context:
The Atkins diet books have sold more than 45 million copies over 40 years, and in the obesity epidemic this diet and accompanying Atkins food products are popular. The diet claims to be effective at producing weight loss despite ad-libitum consumption of fatty meat, butter, and other high-fat dairy products, restricting only the intake of carbohydrates to under 30 g a day. Low-carbohydrate diets have been regarded as fad diets, but recent research questions this view.
Starting point:
A systematic review of low-carbohydrate diets found that the weight loss achieved is associated with the duration of the diet and restriction of energy intake, but not with restriction of carbohydrates. Two groups have reported longer-term randomised studies that compared instruction in the low-carbohydrate diet with a low-fat calorie-reduced diet in obese patients (N Engl J Med 2003; 348: 2082-90; Ann Intern Med 2004; 140: 778-85). Both trials showed better weight loss on the low-carbohydrate diet after 6 months, but no difference after 12 months. WHERE NEXT?: The apparent paradox that ad-libitum intake of high-fat foods produces weight loss might be due to severe restriction of carbohydrate depleting glycogen stores, leading to excretion of bound water, the ketogenic nature of the diet being appetite suppressing, the high protein-content being highly satiating and reducing spontaneous food intake, or limited food choices leading to decreased energy intake. Long-term studies are needed to measure changes in nutritional status and body composition during the low-carbohydrate diet, and to assess fasting and postprandial cardiovascular risk factors and adverse effects. Without that information, low-carbohydrate diets cannot be recommended.
Low-carbohydrate diets have become popular as weight loss techniques. These diets are high in protein, saturated fats, and omega-6 fatty acids. They also lead to a ketogenic state. These factors could lead to increased bone turnover. This study was designed to see whether a low-carbohydrate diet would lead to increased bone turnover in humans.
Thirty patients (15 study subjects and 15 controls) were recruited for this 3-month study. The 15 patients on the diet were instructed to consume less than 20 g of carbohydrates per day for the 1st month and then less than 40 g per day for months 2 and 3. Control subjects had no restrictions on their diet. The primary end point was urinary N-telopeptide (UNTx) at 3 months. Secondary end points included UNTx at 1 month, bone-specific alkaline phosphatase (BSAP) at 1 month, bone turnover ratio (BSAP/UNTx) at 1 month, and weight loss.
The mean UNTx in the study subjects increased by 1.6 [95% confidence interval (CI) +/-22.8] compared with an increase of 1.9 (95% CI +/-17.6) in the controls at 3 months (p=0.86). The mean UNTx decreased by 2.2 (95% CI +/-27.2) and 3.1 (95% CI +/-17.6) at 1 month in the dieters and controls, respectively (p=0.36). The mean BSAP decreased by 0.53 (95% CI +/-2.96) in the dieters and increased by 0.34 (95% CI +/-2.92) in the controls at 1 month (p=0.27). The bone turnover ratio increased by 0.08 (95% CI +/-0.81) in the dieters and by 0.05 (95% CI +/- 0.27) in the controls at 1 month (p=0.78). The dieters lost 6.39 kg versus 1.05 kg for the controls at 3 months (p=0.0008).
Although the patients on the low-carbohydrate diet did lose significantly more weight than the controls did, the diet did not increase bone turnover markers compared with controls at any time point. Further, there was no significant change in the bone turnover ratio compared with controls.
The prevalence of overweight and obesity is increasing dramatically worldwide. As a consequence, bariatric surgery for morbid obesity is in constant development. Although bariatric surgery has proven its efficiency at achieving weight loss and correcting comorbidities, it may cause vitamin deficiencies and subsequent complications. The goal of this review is to assess the impact of obesity surgery on bone metabolism and to analyze the underlying mechanisms and relationships with adipokines. Our review focuses on gastric banding, vertical banded gastroplasty, and gastric bypass.
The articles were located via PubMed database, using the key words "bariatric surgery," "weight loss," "bone loss," and "bone metabolism" and published until May 2006.
Five main studies were reviewed concerning gastric banding and six concerning Roux-en-Y gastric bypass. An early increase in bone markers (formation and resorption) is constantly found, prevailing on bone resorption, and resulting in early bone loss.
According to the few studies available, bone loss frequently occurs after bariatric surgery and particularly in a more pronounced way after gastric bypass, but its clinical significance is still under discussion. In addition, the physiopathology of these changes remains unclear, but could implicate adipokines such as leptin and adiponectin.