Visceral-to-peripheral adiposity ratio: a critical determinant of sex and ethnic differences in cardiovascular risks among Asian Indians and African Creoles in Mauritius.

BACKGROUND/AIMS: Coronary heart disease morbidity and mortality are higher in people of South Asian origin than in those of African origin. We investigated whether as young adults without diabetes, people in Mauritius of South Asian descent (Indians) would show a more adverse cardiovascular risk profile that those of predominantly African descent (Creoles), and whether this could be explained by ethnic differences in visceral adiposity or other fat distribution patterns. METHODS: The study was conducted in 189 young non-physically active adults, with the following measurements conducted after an overnight fast: anthropometry (weight, height, waist circumference), whole-body and regional body composition by dual-energy x-ray absorptiometry, blood pressure, and blood assays for glycemic (glucose and HbA1c) and lipid profile (triglycerides and cholesterols). RESULTS: The results indicate higher serum triglycerides and lower HDL cholesterol in men than in women, and in Indians than in Creoles (p < 0.001). No significant differences due to sex or ethnicity are observed in body mass index and waist circumference, but indices of visceral adiposity (visceral/android, visceral/subcutaneous) and visceral-to-peripheral adiposity ratio (visceral/gynoid, visceral/limb) were significantly higher in men than in women, and in Indians than in Creoles. The significant effects of sex and ethnicity on blood lipid profile were either completely abolished or reduced to a greater extent after adjusting for the ratio of visceral-to-peripheral adiposity than for visceral adiposity per se. CONCLUSIONS: In young adults in Mauritius, Indians show a more adverse pattern of body fat distribution and blood lipid risk profile than Creoles. Differences in their fat distribution patterns, however, only partially explain their differential atherogenic lipid risk profile, amid a greater impact of visceral-to-peripheral adiposity ratio than that of visceral adiposity per se on sex and ethnic differences in cardiovascular risks; the former possibly reflecting the ratio of hazardous (visceral) adiposity and protective (peripheral) superficial subcutaneous adiposity.

Dynamics of Fat Oxidation from Sitting at Rest to Light Exercise in Inactive Young Humans.

Societal erosion of daily life low-level physical activity has had a great influence on the obesity epidemic. Given that low fat oxidation is also a risk factor for obesity, we investigated, in a repeated measures design, the dynamics of fat oxidation from a resting state to a light-intensity leg cycling exercise (0-50 watts) in inactive, healthy young adults. Using indirect calorimetry, energy expenditure and the respiratory quotient (RQ) were assessed in a sitting posture at rest and during a cycling exercise in 35 subjects (20 women). The rate of perceived exhaustion (RPE) was assessed using the Borg Scale. During graded leg cycling, the mean RPE did not exceed values corresponding to the exercise being perceived as 'light'. However, analysis of individual data at 50 watts revealed two distinct subgroups among the subjects: those having RPE values corresponding to the exercise being perceived as 'very light to light' and showing no increase in RQ relative to resting levels, as opposed to an increase in RQ in those who perceived the exercise as being 'somewhat hard to hard' (p < 0.001). Our study in inactive individuals showing that high fat oxidation was maintained during 'light-perceived' physical activity reinforced the potential importance of light physical activity in the prevention of obesity.

Low-carbohydrate ketogenic diets in body weight control: A recurrent plaguing issue of fad diets?

The most appropriate type of diets to maintain or lose body weight over the medium to long term has been a matter of controversy and debates for more than half a century. Both voluntarily and coercive food restriction, resulting in negative energy and macronutrient balance and hence weight loss, have not been designed to be maintained for the long term. By contrast, when a classical and traditional type of alimentation is consumed in ad lib conditions (e.g., the Mediterranean "diet"), it generally provides an appropriate nutritional density of essential macronutrients and micronutrients; it is hence appropriate for long-term use, and it provides several benefits for health if the compliance of the individuals is maintained over time. In this short review, we focus on four specific aspects: first, the need to agree on a clear definition of what is "low" versus "high" in terms of total carbohydrate intake and total fat intakes, both generally inversely related, in a representative individual with a certain lifestyle and a certain body morphology; second, the importance of discussing the duration over which it could be prescribed, that is, acute versus chronic conditions, focusing on the comparison between the fashion and often ephemeral low-carbohydrate diet (acute) with the well-recognized traditional Mediterranean type of alimentation (chronic), which includes lifestyle changes; third, the particular metabolic characteristics induced by the low-carbohydrate (high fat) diet, namely, the scramble up of ketone bodies production. The recent debate on ketogenic diets concern whether or not, in iso-energetic conditions, low-carbohydrate diets would significantly enhance energy expenditure. This is an issue that is more "academic" than practical, on the ground that the putative difference of 100-150 kcal/day or so (in the recent studies) is not negligible but within the inherent error of the methodology used to track total energy expenditure in free living conditions by the doubly labeled water technique. Fourth, the potential medical risks and shortcomings of ingesting (over the long term) low-carbohydrate ketogenic diets could exacerbate underlying renal dysfunction, consecutive to the joint combination of high-fat, high-protein diets, particularly in individuals with obesity. This particular diet promotes metabolic acidosis and renal hyperfiltration, which ultimately may contribute to a significant reduction in life expectancy in middle-age people.

13C/12C breath test ratio after the ingestion of a meal naturally enriched with (13C)carbohydrates is a surrogate marker of insulin resistance and insulin sensitivity in children and adolescents with Type 1 Diabetes.

AIMS: To test the hypotheses that exogenous carbohydrate oxidation affects postprandial glycaemic profiles and 13C/12C breath test could be used for estimating insulin resistance (IR) and insulin sensitivity (IS) in youths with Type 1 Diabetes (T1D). METHODS: Non-randomized, cross-sectional study for repeated measures; fifteen youths (11-15 years) with T1D were enrolled. Respiratory exchanges were measured by indirect calorimetry after the ingestion of a mixed meal [13% protein, 29% fat, 58% carbohydrate (CHO; naturally enriched with [13C]carbohydrates)]. Total and exogenous CHOs oxidation was calculated by indirect calorimetry and 13C/12C breath test. IR and IS were calculated using estimated Glucose Disposal Rate (eGDR) and Insulin Sensitivity Score (ISS). RESULTS: The blood glucose Area Under the Curve (BG-AUC) was significantly associated with the amount of exogenous CHOs oxidized (r = -0.67, p < 0.02) when adjusting for CHOs intake and %fat mass. A direct correlation between eGDR and ISS with exogenous CHOs oxidized (r = 0.70, p < 0.02; r = 0.61, p < 0.05 respectively) and with the differential of 13C/12C enrichment in the expired at breath test (r = 0.59, p < 0.05; r = 0.62, p < 0.05), was found. CONCLUSIONS: Assessing the capacity to oxidize exogenous CHOs (estimated by the differential of 13C/12C enrichment in the expired air at the breath test) could be used as a non-invasive surrogate marker of IR and IS in youths with T1D.

How dieting might make some fatter: modeling weight cycling toward obesity from a perspective of body composition autoregulation.

The notion that dieting makes some people fatter has in the past decade gained considerable interest from both epidemiological predictions and biological plausibility. Several large-scale prospective studies have suggested that dieting to lose weight is associated with future weight gain and obesity, with such predictions being stronger and more consistent among dieters who are in the normal range of body weight rather than in those with obesity. Furthermore, the biological plausibility that dieting predisposes people who are lean (rather than those with overweight or obesity) to regain more body fat than what had been lost (referred to as fat overshooting) has recently gained support from a re-analysis of data on body composition during weight loss and subsequent weight recovery from the classic longitudinal Minnesota Starvation Experiment. These have revealed an inverse exponential relationship between the amount of fat overshot and initial adiposity, and have suggested that a temporal desynchronization in the recoveries of fat and lean tissues, in turn residing in differences in lean-fat partitioning during weight loss vs. during weight recovery (with fat recovery faster than lean tissue recovery) is a cardinal feature of fat overshooting. Within a conceptual framework that integrates the relationship between post-dieting fat overshooting with initial adiposity, the extent of weight loss and the differential lean-fat partitioning during weight loss vs. weight recovery, we describe here a mathematical model of weight cycling to predict the excess fat that could be gained through repeated dieting and multiple weight cycles from a standpoint of body composition autoregulation.

Body composition-derived BMI cut-offs for overweight and obesity in ethnic Indian and Creole urban children of Mauritius.

It is increasingly recognised that the use of BMI cut-off points for diagnosing obesity (OB) and proxy measures for body fatness in a given population needs to take into account the potential impact of ethnicity on the BMI-fat % relationship in order to avoid adiposity status misclassification. This relationship was studied here in 377 Mauritian schoolchildren (200 boys and 177 girls, aged 7-13 years) belonging to the two main ethnic groups: Indian (South Asian descent) and Creole (African/Malagasy descent), with body composition assessed using an isotopic 2H dilution technique as reference. The results indicate that for the same BMI, Indians have more body fat (and less lean mass) than Creoles among both boys and girls: linear regression analysis revealed significantly higher body fat % by 4-5 units (P < 0·001) in Indians than in Creoles across a wide range of BMI (11·6-34·2 kg/m2) and body fat % (5-52 %). By applying Deurenberg's Caucasian-based equation to predict body fat % from WHO-defined BMI thresholds for overweight (OW) and OB, and by recalculating the equivalent BMI values using a Mauritian-specific equation, it is shown that the WHO BMI cut-offs for OB and OW would need to be lowered by 4·6-5·9 units in Indian and 2·0-3·7 units in Creole children in the 7-13-year-old age group. These results have major implications for ethnic-based population research towards improving the early diagnosis of excess adiposity in this multi-ethnic population known to be at high risk for later development of type 2 diabetes and CVD.

Total energy expenditure assessed by doubly labeled water technique and estimates of physical activity in Mauritian children: analysis by gender and ethnicity.

BACKGROUND/OBJECTIVES: In the tropical island of Mauritius, the rise in obesity has accelerated in the past decades, and could be contributed by low physical activity and increased sedentary behavior. The study objectives were to generate the first dataset of total energy expenditure (TEE), to estimate physical activity in Mauritian children, and to explore differences due to gender and ethnicity. SUBJECTS/METHODS: The doubly labeled water (DLW) technique was used to evaluate TEE over 14 days in 56 Mauritian school children (aged 7-11 years) belonging to the two main ethnic groups: Indian (South Asian descent) and Creole (African/Malagasy descent). Physical activity level (PAL) was calculated as the ratio of TEE and resting energy expenditure (using Schofield equations), and daily step counts were measured by accelerometry. Anthropometry and body composition were also assessed. RESULTS: TEE measured by DLW was lower in Mauritian children (by ~155 kcal/d) than that predicted using FAO/WHO/UNU equations for children of the same sex, age, and body size. Furthermore, TEE, as well as PAL and step counts, also differed according to gender (lower in girls than in boys) and to ethnicity (lower in Indians than in Creoles) even after adjusting for differences in body weight and body composition. CONCLUSION: These results in Mauritian children provide the first dataset of objectively measured TEE, from which physical activity is estimated as PAL, and complemented by step counts measurements. They suggest potential gender and ethnic differences in TEE and physical activity that need consideration in developing strategies to counter sedentary behavior and obesity.

Assessment of the Dose-Response Relationship between Meal Protein Content and Postprandial Thermogenesis: Effect of Sex and the Oral Contraceptive Pill.

Implementation of efficacious dietary interventions to regulate energy balance requires understanding of the determinants of individual response. To date, information regarding individual variability in response to elevated meal protein content is lacking. This study investigates whether sex and/or oral contraceptive pill (OCP) use play a role in the response to elevated meal protein in 21 healthy young adults (seven men, seven women not taking OCP, and seven women who were OCP users). Participants consumed each of three standardized isocaloric (590 kcal) meals of differing protein content (11, 23, 31% kcal protein). Resting energy expenditure (EE), respiratory quotient (RQ), hunger and satiety were measured at baseline (fasting) and during 180 min postprandial. Whilst significant dose-response increases in EE were observed in men, meal protein-induced EE in women without OCP reached a maximum at <23% protein. Women taking OCP reported lower postprandial fullness than women without OCP, despite similar body size, but also, most notably, no significant difference in EE response between any of the meals. Whilst the mechanisms underpinning this thermogenic inflexibility in response across a wide-range (three-fold) of protein meal content require further investigation, this highlights the need for careful consideration of factors that may influence an individual's metabolic response to dietary interventions aimed at optimising postprandial thermogenesis for body weight regulation.

Comparison of Conventional and Individualized 1-MET Values for Expressing Maximum Aerobic Metabolic Rate and Habitual Activity Related Energy Expenditure.

The maximum aerobic metabolic rate can be expressed in multiple metabolically equivalent tasks (MET), i.e., METmax. The purpose was to quantify the error when the conventional (3.5 mL∙kg-1∙min-1) compared to an individualized 1-MET-value is used for calculating METmax and estimating activity energy expenditure (AEE) in endurance-trained athletes (END) and active healthy controls (CON). The resting metabolic rate (RMR, indirect calorimetry) and aerobic metabolic capacity (spiroergometry) were assessed in 52 END (46% male, 27.9 ± 5.7 years) and 53 CON (45% male, 27.3 ± 4.6 years). METmax was calculated as the ratio of VO2max over VO2 during RMR (METmax_ind), and VO2max over the conventional 1-MET-value (METmax_fix). AEE was estimated by multiplying published MET values with the individual and conventional 1-MET-values. Dependent t-tests were used to compare the different modes for calculating METmax and AEE (α = 0.05). In women and men CON, men END METmax_fix was significantly higher than METmax_ind (p < 0.01), whereas, in women END, no difference was found (p > 0.05). The conventional 1-MET-value significantly underestimated AEE in men and women CON, and men END (p < 0.05), but not in women END (p > 0.05). The conventional 1-MET-value appears inappropriate for determining the aerobic metabolic capacity and AEE in active and endurance-trained persons.

European Practical and Patient-Centred Guidelines for Adult Obesity Management in Primary Care.

The first contact for patients with obesity for any medical treatment or other issues is generally with General Practitioners (GPs). Therefore, given the complexity of the disease, continuing GPs' education on obesity management is essential. This article aims to provide obesity management guidelines specifically tailored to GPs, favouring a practical patient-centred approach. The focus is on GP communication and motivational interviewing as well as on therapeutic patient education. The new guidelines highlight the importance of avoiding stigmatization, something frequently seen in different health care settings. In addition, managing the psychological aspects of the disease, such as improving self-esteem, body image and quality of life must not be neglected. Finally, the report considers that achieving maximum weight loss in the shortest possible time is not the key to successful treatment. It suggests that 5-10% weight loss is sufficient to obtain substantial health benefits from decreasing comorbidities. Reducing waist circumference should be considered even more important than weight loss per se, as it is linked to a decrease in visceral fat and associated cardiometabolic risks. Finally, preventing weight regain is the cornerstone of lifelong treatment, for any weight loss techniques used (behavioural or pharmaceutical treatments or bariatric surgery).

The case of GWAS of obesity: does body weight control play by the rules?

As yet, genome-wide association studies (GWAS) have not added much to our understanding of the mechanisms of body weight control and of the etiology of obesity. This shortcoming is widely attributed to the complexity of the issues. The appeal of this explanation notwithstanding, we surmise that (i) an oversimplification of the phenotype (namely by the use of crude anthropometric traits) and (ii) a lack of sound concepts of body weight control and, thus, a lack of a clear research focus have impeded better insights most. The idea of searching for polygenetic mechanisms underlying common forms of obesity was born out of the impressive findings made for monogenetic forms of extreme obesity. In the case of common obesity, however, observational studies on normal weight and overweight subjects never provided any strong evidence for a tight internal control of body weight. In addition, empirical studies of weight changes in normal weight and overweight subjects revealed an intra-individual variance that was similar to inter-individual variance suggesting the absence of tight control of body weight. Not least, this lack of coerciveness is reflected by the present obesity epidemic. Finally, data on detailed body composition highlight that body weight is too heterogeneous a phenotype to be controlled as a single entity. In summary GWAS of obesity using crude anthropometric traits have likely been misled by popular heritability estimates that may have been inflated in the first place. To facilitate more robust and useful insights into the mechanisms of internal control of human body weight and, consequently, the genetic basis of obesity, we argue in favor of a broad discussion between scientists from the areas of integrative physiologic and of genomics. This discussion should aim at better conceived studies employing biologically more meaningful phenotypes based on in depth body composition analysis. To advance the scientific community-including the editors of our top journals-needs a re-launch of future GWAS of obesity.

The contribution of Swiss scientists to the assessment of energy metabolism.

Although Switzerland is considered a small country, it has its share in discoveries, inventions and developments for the assessment of energy metabolism. This includes seminal contributions to respiratory and metabolic physiology and to devices for measuring energy expenditure by direct and indirect calorimetry in vivo in humans and small animals (as well as in vitro in organs/tissues), for the purpose of evaluating the basic nutritional requirements. A strong momentum came during World War II when it was necessary to evaluate the energy requirements of soldiers protecting the country by assessing their energy expenditure, as well as to determine the nutritional needs of the Swiss civil population in time of war when food rationing was necessary to ensure national neutrality and independence. A further impetus came in the 1970s at the start of the obesity epidemics, toward a better understanding of the metabolic basis of obesity, ranging from the development of whole-body concepts to molecular mechanisms. In a trip down memory lane, this review focuses on some of the earlier leading Swiss scientists who have contributed to a better understanding of the field.

Collateral fattening in body composition autoregulation: its determinants and significance for obesity predisposition.

Collateral fattening refers to the process whereby excess fat is deposited as a result of the body's attempt to counter a deficit in lean mass through overeating. Its demonstration and significance to weight regulation and obesity can be traced to work on energy budget strategies in growing mammals and birds, and to men recovering from experimental starvation. The cardinal features of collateral fattening rests upon (i) the existence of a feedback system between lean tissue and appetite control, with lean tissue deficit driving hyperphagia, and (ii) upon the occurrence of a temporal desynchronization in the recovery of body composition, with complete recovery of fat mass preceeding that of lean mass. Under these conditions, persistent hyperphagia driven by the need to complete the recovery of lean tissue will result in the excess fat deposition (hence collateral fattening) and fat overshooting. After reviewing the main lines of evidence for the phenomenon of collateral fattening in body composition autoregulation, this article discusses the causes and determinants of the desynchronization in fat and lean tissue recovery leading to collateral fattening and fat overshooting, and points to their significance in the mechanisms by which dieting, developmental programming and sedentariness predispose to obesity.

Oral Contraceptive Pill Alters Acute Dietary Protein-Induced Thermogenesis in Young Women.

OBJECTIVE: There is much interest in the role of dietary protein for weight control. However, there remains a need to characterize individual determinants of the thermogenic effects of protein. This study aimed to investigate the influence of menstrual cycle phase and the combined, monophasic oral contraceptive pill on the thermogenic response to a standardized high-protein (HP) versus normal-protein (NP) meal. METHODS: Following an overnight fast, resting energy expenditure (EE) was measured in 16 healthy young women (8 taking and 8 not taking the pill) and 8 men for 30 minutes pre ingestion and 3 hours post ingestion of a NP (11%) or HP (24%) meal. RESULTS: There was no effect of menstrual phase or contraceptive pill use on fasting EE or NP response. However, HP increased EE significantly more than NP in women not taking the oral contraceptive pill and in men, but not in women taking the pill. CONCLUSIONS: This study shows an absence of the greater thermic effect of HP versus NP in women taking the oral contraceptive pill and has important implications regarding the effectiveness of HP for body weight regulation in women. With current obesity treatment/prevention strategies remaining largely ineffective, understanding the relationship between oral contraceptive pill use and protein-induced thermogenesis may enable the successful recalibration of existing dietary recommendations.

Issues in Continuous 24-h Core Body Temperature Monitoring in Humans Using an Ingestible Capsule Telemetric Sensor.

BACKGROUND: There is increasing interest in the use of pill-sized ingestible capsule telemetric sensors for assessing core body temperature (Tc) as a potential indicator of variability in metabolic efficiency and thrifty metabolic traits. The aim of this study was to investigate the feasibility and accuracy of measuring Tc using the CorTemp® system. METHODS: Tc was measured over an average of 20 h in 27 human subjects, with measurements of energy expenditure made in the overnight fasted state at rest, during standardized low-intensity physical activity and after a 600 kcal mixed meal. Validation of accuracy of the capsule sensors was made ex vivo against mercury and electronic thermometers across the physiological range (35-40°C) in morning and afternoon of 2 or 3 consecutive days. Comparisons between capsule sensors and thermometers were made using Bland-Altman analysis. Systematic bias, error, and temperature drift over time were assessed. RESULTS: The circadian Tc profile classically reported in free-living humans was confirmed. Significant increases in Tc (+0.2°C) were found in response to low-power cycling at 40-50 W (~3-4 METs), but no changes in Tc were detectable during low-level isometric leg press exercise (<2 METs) or during the peak postprandial thermogenesis induced by the 600 kcal meal. Issues of particular interest include fast "turbo" gut transit with expulsion time of <15 h after capsule ingestion in one out of every five subjects and sudden erratic readings in teletransmission of Tc. Furthermore, ex vivo validation revealed a substantial mean bias (exceeding ±0.5°C) between the Tc capsule readings and mercury or electronic thermometers in half of the capsules. When examined over 2 or 3 days, the initial bias (small or large) drifted in excess of ±0.5°C in one out of every four capsules. CONCLUSION: Since Tc is regulated within a very narrow range in the healthy homeotherm's body (within 1°C), physiological investigations of Tc require great accuracy and precision (better than 0.1°C). Although ingestible capsule methodology appears of great interest for non-invasively monitoring the transit gut temperature, new technology requires a reduction in the inherent error of measurement and elimination of temperature drift and warrants more interlaboratory investigation on the above factors.