Energy balance and body-weight stability: impact of gene-environment interactions

The Implication of a Polymorphism in the Methylenetetrahydrofolate Reductase Gene in Homocysteine Metabolism and Related Civilisation Diseases

Methylenetetrahydrofolate reductase (MTHFR) is a key regulatory enzyme in the one-carbon cycle. This enzyme is essential for the metabolism of methionine, folate, and RNA, as well as for the production of proteins, DNA, and RNA. MTHFR catalyses the irreversible conversion of 5,10-methylenetetrahydrofolate to its active form, 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. Numerous variants of the MTHFR gene have been recognised, among which the C677T variant is the most extensively studied. The C677T polymorphism, which results in the conversion of valine to alanine at codon 222, is associated with reduced activity and an increased thermolability of the enzyme. Impaired MTHFR efficiency is associated with increased levels of homocysteine, which can contribute to increased production of reactive oxygen species and the development of oxidative stress. Homocysteine is acknowledged as an independent risk factor for cardiovascular disease, while chronic inflammation serves as the common underlying factor among these issues. Many studies have been conducted to determine whether there is an association between the C677T polymorphism and an increased risk of cardiovascular disease, hypertension, diabetes, and overweight/obesity. There is substantial evidence supporting this association, although several studies have concluded that the polymorphism cannot be reliably used for prediction. This review examines the latest research on MTHFR polymorphisms and their correlation with cardiovascular disease, obesity, and epigenetic regulation.

How Much and What: Using a Buffet to Determine Self-regulation of Food Intake Among Young School-Age Children

Energy compensation indices are commonly used to examine self-regulation of food intake in children. However, previous studies failed to consider children's ability to self-regulate under complete autonomy. This study examined self-regulation of food intake among young children and the effect of calorie manipulation on food/nutrient intake using an unlimited lunch buffet paradigm. Participants were 66 children (M^age = 6.14, SD = 1.15 years; 68.2% male; 89.4% Latinx; 59.1% overweight/obese [OV/OB]). Children participated in a crossover research trial, one week apart. Participants consumed 2 different types of preloads followed by an ad-libitum lunch during each trial. A compensation index (COMPX) was calculated to identify the level of self-regulation in food intake. Food/nutrient intake was compared between both sessions. Results indicated OV/OB children showed poorer self-regulation compared to healthy weight children (t=2.19, p = .032; Hedges' g = 0.55). There were significant differences in food intake/selection between OV/OB and healthy weight groups. OV/OB children consumed a higher amount of calorie, fat, and cholesterol after the high energy preload compared to healthy weight children (d's range: 0.31-0.48). Our findings support differences between the amount of self-regulation between normal and OV/OB children as well as the items they select in order to compensate.

Cafeteria diet induces global and Slc27a3-specific hypomethylation in male Wistar rats

Increased visceral adipose tissue (VAT) is associated with metabolic dysfunction, while subcutaneous adipose tissue (SAT) is considered protective. The mechanisms underlying these differences are not fully elucidated. This study aimed to investigate molecular differences in VAT and SAT of male Wistar rats fed a cafeteria diet (CD) or a standard rodent diet (STD) for three months. The expression of fatty acid metabolism genes was analysed by quantitative real-time PCR. Global and gene-specific DNA methylation was quantified using the Imprint® Methylated DNA Quantification Kit and pyrosequencing, respectively. Bodyweight, retroperitoneal fat mass, insulin resistance, leptin and triglyceride concentrations and adipocyte hypertrophy were higher in CD- compared to STD-fed rats. The expression of solute carrier family 27 member 3 (Slc27a3), a fatty acid transporter, was 9.6-fold higher in VAT and 6.3-fold lower in SAT of CD- versus STD-fed rats. Taqman probes confirmed increased Slc27a3 expression, while pyrosequencing showed Slc27a3 hypomethylation in VAT of CD- compared to STD-fed rats. The CD decreased global methylation in both VAT and SAT, although no depot differences were observed. Dysregulated fatty acid influx in VAT, in response to a CD, provides insight into the mechanisms underlying depot-differences in adipose tissue expansion during obesity and metabolic disease.

Abbreviations: CD: cafeteria diet; E2F1: E2F Transcription Factor 1; EMSA: electrophoretic mobility shift assay; EGFR: epidermal growth factor receptor; GCF: GC-Rich Sequence DNA-Binding Factor; HOMA-IR: Homeostasis model for insulin resistance; NKX2-1: NK2 homeobox 1; PCR: Polymerase chain reaction; qRT-PCR: quantitative real-time PCR; RF: retroperitoneal fat; SAT: subcutaneous adipose tissue; Slc27a3: solute carrier family 27 member 3; STD: standard diet; TNFα: tumour necrosis factor alpha; TTS: transcriptional start site; T2D: Type 2 Diabetes; VAT: visceral adipose tissue; WT1 I: Wilms’ tumour protein 1

Attenuating the Biologic Drive for Weight Regain Following Weight Loss: Must What Goes Down Always Go Back Up?

Metabolic adaptations occur with weight loss that result in increased hunger with discordant simultaneous reductions in energy requirements—producing the so-called energy gap in which more energy is desired than is required. The increased hunger is associated with elevation of the orexigenic hormone ghrelin and decrements in anorexigenic hormones. The lower total daily energy expenditure with diet-induced weight loss results from (1) a disproportionately greater decrease in circulating leptin and resting metabolic rate (RMR) than would be predicted based on the decline in body mass, (2) decreased thermic effect of food (TEF), and (3) increased energy efficiency at work intensities characteristic of activities of daily living. These metabolic adaptations can readily promote weight regain. While more experimental research is needed to identify effective strategies to narrow the energy gap and attenuate weight regain, some factors contributing to long-term weight loss maintenance have been identified. Less hunger and greater satiation have been associated with higher intakes of protein and dietary fiber, and lower glycemic load diets. High levels of physical activity are characteristic of most successful weight maintainers. A high energy flux state characterized by high daily energy expenditure and matching energy intake may attenuate the declines in RMR and TEF, and may also result in more accurate regulation of energy intake to match daily energy expenditure.

Partitioning the variance in calorie restriction-induced weight and fat loss in outbred mice

OBJECTIVE

An increased understanding of the factors influencing interindividual variation in calorie restriction (CR)-induced weight loss is necessary to combat the current obesity epidemic. This study investigated the partitioning of the phenotypic variation in CR-induced wight loss.

METHODS

Two generations of male and female outbred MF1 mice raised by their biological mother or a foster mother were studied. Mice were exposed to 4 weeks of 30% CR when 6 months old.

RESULTS

Heritability was estimated at 0.43 ± 0.12 for CR-induced changes in body mass and 0.24 ± 0.10 for fat mass using mid-parent-offspring regressions. No significant relationships between weight loss in fathers or foster mothers and offspring were observed. Partitioning of phenotypic variance in weight loss using maximum likelihood modeling indicated 19 ± 17% of the variation could be attributed to additive genetic effects, 8 ± 14% to maternal effects during pregnancy, and <1% to maternal effects during lactation. A narrow-sense heritability around 0.50 was observed for ad libitum food intake and general activity.

CONCLUSIONS

A large part of individual variation in CR-induced weight loss could be attributed to additive genetic and maternal effects during pregnancy, but not to maternal effects in lactation. Genetic differences in food intake and general activity may play a role in determining these effects.

The Local Food Environment and Body Mass Index among the Urban Poor in Accra, Ghana

Obesity in the sub-Saharan Africa region has been portrayed as a problem of affluence, partly because obesity has been found to be more common in urban areas and among the rich. Recent findings, however, reveal rising prevalence among the poor particularly the urban poor. A growing body of literature mostly in Western countries shows that obesity among the poor is partly the result of an obesogenic-built environment. Such studies are lacking in the African context. This study examines the characteristics of the local food environment in an urban poor setting in Accra, Ghana and further investigates the associated risk of obesity for residents. Data on the local food environment was collected using geographic positioning system (GPS) technology. The body mass indices (BMI) of females (15-49 years) and males (15-59 years) were calculated from measured weight and height. Data on the socio-demographic characteristics and lifestyle behaviors of respondents was also collected through a household survey. Spatial analysis tools were used to examine the characteristics of the local food environment while the influence of the food environment on BMI was examined using a two-level multilevel model. The measures of the food environment constituted the level 2 factors while individual socio-demographic characteristics and lifestyle behaviors constituted the level 1 factors. The local food environment in the study communities is suggestive of an obesogenic food environment characterized by an abundance of out-of-home cooked foods, convenience stores, and limited fruits and vegetables options. The results of the multilevel analysis reveal a 0.2 kg/m(2) increase in BMI for every additional convenience store and a 0.1 kg/m(2) reduction in BMI for every out-of-home cooked food place available in the study area after controlling for individual socio-demographic characteristics, lifestyle behaviors, and community characteristics. The findings of this study indicate that the local food environment in urban poor Accra is associated with increased risk of obesity through providing access to convenience stores. In order to reduce the risk of obesity in these urban poor communities, there is the need to regulate the availability of and access to convenience stores while also encouraging healthier offerings in convenience stores.

Health-Related Physical Fitness in Healthy Untrained Men: Effects on VO2max, Jump Performance and Flexibility of Soccer and Moderate-Intensity Continuous Running

The purpose of this study was to determine the effects of recreational soccer (SOC) compared to moderate-intensity continuous running (RUN) on all health-related physical fitness components in healthy untrained men. Sixty-nine participants were recruited and randomly assigned to one of three groups, of which sixty-four completed the study: a soccer training group (SOC; n = 20, 34±4 (means±SD) years, 78.1±8.3 kg, 179±4 cm); a running group (RUN; n = 21, 32±4 years, 78.0±5.5 kg, 179±7 cm); or a passive control group (CON; n = 23, 30±3 years, 76.6±12.0 kg, 178±8 cm). The training intervention lasted 12 weeks and consisted of three 60-min sessions per week. All participants were tested for each of the following physical fitness components: maximal aerobic power, minute ventilation, maximal heart rate, squat jump (SJ), countermovement jump with arm swing (CMJ), sit-and-reach flexibility, and body composition. Over the 12 weeks, VO2max relative to body weight increased more (p<0.05) in SOC (24.2%, ES = 1.20) and RUN (21.5%, ES = 1.17) than in CON (-5.0%, ES = -0.24), partly due to large changes in body mass (-5.9, -5.7 and +2.6 kg, p<0.05 for SOC, RUN and CON, respectively). Over the 12 weeks, SJ and CMJ performance increased more (p<0.05) in SOC (14.8 and 12.1%, ES = 1.08 and 0.81) than in RUN (3.3 and 3.0%, ES = 0.23 and 0.19) and CON (0.3 and 0.2%), while flexibility also increased more (p<0.05) in SOC (94%, ES = 0.97) than in RUN and CON (0-2%). In conclusion, untrained men displayed marked improvements in maximal aerobic power after 12 weeks of soccer training and moderate-intensity running, partly due to large decreases in body mass. Additionally soccer training induced pronounced positive effects on jump performance and flexibility, making soccer an effective broad-spectrum fitness training intervention.

C677T gene polymorphism of MTHFR and metabolic syndrome: response to dietary intervention

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms were found associated with body mass index (BMI)-defined obesity and lean mass. The aim of our study was to examine the role of the C677T MTHFR gene polymorphism in the response to diet in the management of metabolic syndrome. We investigated the body composition and metabolic factor changes after an hysocaloric balanced diet (HBD), in Italian obese women affected by metabolic syndrome (MS).

METHODS

Forty four obese women affected by MS were eligible for the study. A HBD for 12 weeks was assigned. Study participation included a complete screening for dietary habits, anthropometry, body composition, blood biochemical markers and C677T MTHFR polymorphism genotyping. The study has been registrated by ClinicalTrials.gov Id: NCT01890070.

RESULTS

The highest number of responders to HBD nutritional intervention were T(-) carriers (p ≤ 0.05). In the 81% of the total population a loss of Total Body Lean was observed. A significative loss (p ≤ 0.05) of Total Body Lean was observed in the 47% of T(-) carriers and in the 53% of T(+) carriers. Diastolic and systolic blood pressure, and waist circumference were reduced (p ≤ 0.05). The prevalence of MS parameters decreased by 84% for systolic and diastolic blood pressure; 79,5% for HDL cholesterol, 82% for fasting glucose and 77% for triglycerides.

CONCLUSIONS

MTHFR genetic variations analysis would be an innovative tool for the nutritional assessment. Our data provide the basis for personalized dietary recommendations based on the individual's genetic makeup and nutritional status.

TRIAL REGISTRATION

The study has been registrated by ClinicalTrials.gov Id: NCT01890070.

Distinct associations between energy balance and the sleep characteristics slow wave sleep and rapid eye movement sleep

CONTEXT

Epidemiologically, an inverse relationship between body mass index (BMI) and sleep duration is observed. Intra-individual variance in the amount of slow wave sleep (SWS) or rapid eye movement (REM) sleep has been related to variance of metabolic and endocrine parameters, which are risk factors for the disturbance of energy balance (EB).

OBJECTIVE

To investigate inter-individual relationships between EB (EB= energy intake-energy expenditure∣, MJ/24 h), SWS or REM sleep, and relevant parameters in normal-weight men during two 48 h stays in the controlled environment of a respiration chamber.

SUBJECTS AND METHODS

A total of 16 men (age 23±3.7 years, BMI 23.9±1.9 kg m(-2)) stayed in the respiration chamber twice for 48 h to assure EB. Electroencephalography was used to monitor sleep (2330-0730 hrs). Hunger and fullness were scored by visual analog scales; mood was determined by State Trait Anxiety Index-state and food reward by liking and wanting. Baseline blood and salivary samples were collected before breakfast. Subjects were fed in EB, except for the last dinner, when energy intake was ad libitum.

RESULTS

The subjects slept on average 441.8±49 min per night, and showed high within-subject reliability for the amount of SWS and REM sleep. Linear regression analyses showed that EB was inversely related to the amount of SWS (r=-0.43, P<0.03), and positively related to the amount of REM sleep (r=0.40, P<0.05). Relevant parameters such as hunger, reward, stress and orexigenic hormone concentrations were related to overeating, as well as to the amount of SWS and REM sleep, however, after inclusion of these parameters in a multiple regression, the amount of SWS and REM sleep did not add to the explained variance of EB, which suggests that due to their individual associations, these EB parameters are mediator variables.

CONCLUSION

A positive EB due to overeating, was explained by a smaller amount of SWS and higher amount of REM sleep, mediated by hunger, fullness, State Trait Anxiety Index-state scores, glucose/insulin ratio, and ghrelin and cortisol concentrations.

Protocol for the modeling the epidemiologic transition study: a longitudinal observational study of energy balance and change in body weight, diabetes and cardiovascular disease risk

BACKGROUND

The prevalence of obesity has increased in societies of all socio-cultural backgrounds. To date, guidelines set forward to prevent obesity have universally emphasized optimal levels of physical activity. However there are few empirical data to support the assertion that low levels of energy expenditure in activity is a causal factor in the current obesity epidemic are very limited.

METHODS/DESIGN

The Modeling the Epidemiologic Transition Study (METS) is a cohort study designed to assess the association between physical activity levels and relative weight, weight gain and diabetes and cardiovascular disease risk in five population-based samples at different stages of economic development. Twenty-five hundred young adults, ages 25-45, were enrolled in the study; 500 from sites in Ghana, South Africa, Seychelles, Jamaica and the United States. At baseline, physical activity levels were assessed using accelerometry and a questionnaire in all participants and by doubly labeled water in a subsample of 75 per site. We assessed dietary intake using two separate 24-hour recalls, body composition using bioelectrical impedance analysis, and health history, social and economic indicators by questionnaire. Blood pressure was measured and blood samples collected for measurement of lipids, glucose, insulin and adipokines. Full examination including physical activity using accelerometry, anthropometric data and fasting glucose will take place at 12 and 24 months. The distribution of the main variables and the associations between physical activity, independent of energy intake, glucose metabolism and anthropometric measures will be assessed using cross-section and longitudinal analysis within and between sites.

DISCUSSION

METS will provide insight on the relative contribution of physical activity and diet to excess weight, age-related weight gain and incident glucose impairment in five populations' samples of young adults at different stages of economic development. These data should be useful for the development of empirically-based public health policy aimed at the prevention of obesity and associated chronic diseases.

Set points, settling points and some alternative models: theoretical options to understand how genes and environments combine to regulate body adiposity

The close correspondence between energy intake and expenditure over prolonged time periods, coupled with an apparent protection of the level of body adiposity in the face of perturbations of energy balance, has led to the idea that body fatness is regulated via mechanisms that control intake and energy expenditure. Two models have dominated the discussion of how this regulation might take place. The set point model is rooted in physiology, genetics and molecular biology, and suggests that there is an active feedback mechanism linking adipose tissue (stored energy) to intake and expenditure via a set point, presumably encoded in the brain. This model is consistent with many of the biological aspects of energy balance, but struggles to explain the many significant environmental and social influences on obesity, food intake and physical activity. More importantly, the set point model does not effectively explain the 'obesity epidemic'--the large increase in body weight and adiposity of a large proportion of individuals in many countries since the 1980s. An alternative model, called the settling point model, is based on the idea that there is passive feedback between the size of the body stores and aspects of expenditure. This model accommodates many of the social and environmental characteristics of energy balance, but struggles to explain some of the biological and genetic aspects. The shortcomings of these two models reflect their failure to address the gene-by-environment interactions that dominate the regulation of body weight. We discuss two additional models--the general intake model and the dual intervention point model--that address this issue and might offer better ways to understand how body fatness is controlled.

The biological control of voluntary exercise, spontaneous physical activity and daily energy expenditure in relation to obesity: human and rodent perspectives

Mammals expend energy in many ways, including basic cellular maintenance and repair, digestion, thermoregulation, locomotion, growth and reproduction. These processes can vary tremendously among species and individuals, potentially leading to large variation in daily energy expenditure (DEE). Locomotor energy costs can be substantial for large-bodied species and those with high-activity lifestyles. For humans in industrialized societies, locomotion necessary for daily activities is often relatively low, so it has been presumed that activity energy expenditure and DEE are lower than in our ancestors. Whether this is true and has contributed to a rise in obesity is controversial. In humans, much attention has centered on spontaneous physical activity (SPA) or non-exercise activity thermogenesis (NEAT), the latter sometimes defined so broadly as to include all energy expended due to activity, exclusive of volitional exercise. Given that most people in Western societies engage in little voluntary exercise, increasing NEAT may be an effective way to maintain DEE and combat overweight and obesity. One way to promote NEAT is to decrease the amount of time spent on sedentary behaviours (e.g. watching television). The effects of voluntary exercise on other components of physical activity are highly variable in humans, partly as a function of age, and have rarely been studied in rodents. However, most rodent studies indicate that food consumption increases in the presence of wheels; therefore, other aspects of physical activity are not reduced enough to compensate for the energetic cost of wheel running. Most rodent studies also show negative effects of wheel access on body fat, especially in males. Sedentary behaviours per se have not been studied in rodents in relation to obesity. Several lines of evidence demonstrate the important role of dopamine, in addition to other neural signaling networks (e.g. the endocannabinoid system), in the control of voluntary exercise. A largely separate literature points to a key role for orexins in SPA and NEAT. Brain reward centers are involved in both types of physical activities and eating behaviours, likely leading to complex interactions. Moreover, voluntary exercise and, possibly, eating can be addictive. A growing body of research considers the relationships between personality traits and physical activity, appetite, obesity and other aspects of physical and mental health. Future studies should explore the neurobiology, endocrinology and genetics of physical activity and sedentary behaviour by examining key brain areas, neurotransmitters and hormones involved in motivation, reward and/or the regulation of energy balance.

Genetic associations with acute stress-related changes in eating in the absence of hunger

BACKGROUND

Acute psychological stress is associated with eating in the absence of hunger.

OBJECTIVE

To investigate if BclI and FTO polymorphisms are associated with eating in the absence of hunger as a result of acute psychological stress.

METHODS

FTO (rs9939609) and BclI were genotyped in 98 subjects (BMI=23.9+/-3.3kg/m(2)). In a randomized crossover design, the 'eating in absence of hunger' protocol was measured as a function of acute stress vs. a control task and of STAI (State Trait Anxiety Index) state scores.

RESULTS

In comparison with the FTO T allele, the A allele was associated with an increased feelings of hunger after food intake in the stress (11+/-10 vs. 18+/-15, p<0.01) and control condition (12+/-9 vs. 16+/-12, p<0.05), even though food intake was not different. For the first time, it was observed that in comparison to the BclI C/C genotype, the BclI G/G genotype was associated with higher STAI states scores at 0, 10, and 20min after the stress condition (30.8+/-6.4 vs. 36.3+/-8.2; 28.3+/-5.5 vs. 32.3+/-7.5; 27.7+/-6.1 vs. 31.2+/-7.5, p<0.05). Additionally, the BclI G/G genotype was associated with a larger difference in energy intake between the stress and control condition, in comparison with the BclI C/C genotype (136.6+/-220.4 vs. 29.4+/-176.3kJ, p<0.04).

CONCLUSION

In concordance with previous studies, the FTO A allele is related to a lower feeling of hunger after a standardized meal. For the first time, the BclI G/G genotype is shown to be associated with increased sensitivity to psychological stress, and increased eating in the absence of hunger after stress.

PRACTICE IMPLICATIONS

Interventions to reduce body weight should consider the subjects' genetic background.

Dietary starch type affects body weight and glycemic control in freely fed but not energy-restricted obese rats

This study comprised 2 experiments that tested the hypothesis that a high-amylose starch diet (AMO) would improve body weight and glycemic control relative to a high-amylopectin starch diet (AMN) in rats with diet-induced obesity. After inducing obesity with a high-fat and -energy diet (Expt. 1), male Sprague-Dawley rats (n = 46) were divided into 4 groups and given free or restricted access to either an AMN or an AMO diet for 4 wk (Expt. 2). After 3 wk, rats from each group underwent an oral glucose tolerance test. At the end of the experiment, food-deprived rats were killed by decapitation and blood and tissues were collected for analyses. AMO led to lower total energy intake, weight gain, fat pad mass, and glycemic response but higher insulin sensitivity index than AMN, only when consumed ad libitum (AL) (P < 0.05). AMO led to higher glucagon-like peptide-1 and peptide YY responses and mRNA levels, independent of feeding paradigm (P < 0.01). The mRNA levels of key neuropeptide systems involved in the regulation of food intake were affected only by energy restriction. On the other hand, AMO resulted in higher expression of uncoupling protein-1 in the brown adipose tissue than AMN in rats that consumed food AL (P < 0.05). The effects of AMO appear to be mediated by its high resistant starch content rather than its glycemic index. We conclude that starches high in AMO can be effective in weight and glycemic control in obesity.

Acute stress-related changes in eating in the absence of hunger

Obesity results from chronic deregulation of energy balance, which may in part be caused by stress. Our objective was to investigate the effect of acute and psychological stress on food intake, using the eating in the absence of hunger paradigm, in normal and overweight men and women (while taking dietary restraint and disinhibition into account). In 129 subjects (BMI = 24.5 +/- 3.4 kg/m(2) and age = 27.6 +/- 8.8 years), scores were determined on the Three Factor Eating Questionnaire (dietary restraint = 7.2 +/- 4.4; disinhibition = 4.5 +/- 2.6; feeling of hunger = 3.9 +/- 2.6) and State-Trait Anxiety Inventory (trait score = 31.7 +/- 24.2). In a randomized crossover design, the "eating in absence of hunger" protocol was measured as a function of acute stress vs. a control task and of state anxiety scores. Energy intake from sweet foods (708.1 kJ vs. 599.4 kJ, P < 0.03) and total energy intake (965.2 kJ vs. 793.8 kJ, P < 0.01) were significantly higher in the stress condition compared to the control condition. Differences in energy intake between the stress and control condition were a function of increase in state anxiety scores during the stress task (Delta state anxiety scores) (R(2) = 0.05, P < 0.01). This positive relationship was stronger in subjects with high disinhibition scores (R(2) = 0.12, P < 0.05). Differences in state anxiety scores were a function of trait anxiety scores (R(2) = 0.07, P < 0.05). We conclude that acute psychological stress is associated with eating in the absence of hunger, especially in vulnerable individuals characterized by disinhibited eating behavior and sensitivity to chronic stress.

Polymorphisms in the serotonin reuptake transporter gene modify the consequences of social status on metabolic health in female rhesus monkeys

Individuals vary substantially in their vulnerability to physical and psychosocial stressors. The causes of such variation in susceptibility to stress are poorly understood, but are thought to relate in part to genetic factors. The present study evaluated the extent to which polymorphisms in the gene encoding the serotonin reuptake transporter (5HTTLPR or SERT) modulated physiologic responses to the imposition of psychosocial stress (social reorganization and subordinate social status) in female rhesus monkeys. Forty females, drawn from the middle ranking genealogies of several large social groups, were reorganized into eight groups containing 5 monkeys each; four groups were comprised entirely of animals homogeneous for the long promoter variant in the SERT gene (l/l), while the other four groups had monkeys with at least one allele of the short promoter variant (l/s or s/s). Females were sequentially introduced into these new groups in random order and dominance ranks were established within several days. During the ensuing 6 weeks, dominant monkeys exhibited elevated rates of aggression while subordinates displayed high rates of submission. Notably, females with the s-variant SERT genotype, collapsed across social status positions, exhibited the highest overall rates of both aggression and submission. Although neither social status nor SERT genotype influenced morning cortisol concentrations, glucocorticoid negative feedback was reduced significantly in subordinate compared to dominant females irrespective of genotype. All animals lost weight and abdominal fat across the experiment. However, decreases were greatest in subordinates, regardless of genotype, and least in dominant females with the l/l genotype. Serum concentrations of insulin, glucose, and ghrelin decreased significantly during the group formation process, effects that were independent of genotype or social status. In contrast, social status and genotype interacted to influence changes in serum concentrations of leptin and triiodothyronine (T3), as dominant, l/l females had the highest levels while subordinate s-variant females had the lowest levels. The order in which a female was introduced to her group generally predicted her eventual social rank. However, rank was additionally predicted by pre-experimental T3 and abdominal fat values, but only in the l/l animals. While these findings must be replicated with a larger sample size, the data suggest that the s-variant SERT genotype confers increased vulnerability to the adverse effects of psychosocial stress associated with subordinate status while the l/l genotype benefits the most from the absence of stress conferred by dominant social status. These findings suggest that genetic factors modify the responses of monkeys to social subordination and perhaps other psychosocial stressors.

Gene-diet interactions in childhood obesity: paucity of evidence as the epidemic of childhood obesity continues to rise

Childhood obesity is growing rapidly worldwide. Although there have been enormous advances in the genetic underpinnings of obesity in recent years, the pathways that lead to obesity are still not completely understood. One of the ongoing challenges is the lack of a comprehensive definition of the obese phenotype that encompasses intermediary phenotypic expressions of biological and behavioral nature. Interactions between genetic and environmental factors, including nutrient exposures and dietary behaviors, can influence the development of the obese phenotype. Specifically, genes play a decisive role in the etiology of childhood obesity under the permissive circumstances of an obesogenic environment (increase in energy intake with a decrease in physical activity). Like many diseases, the causes of obesity are complex and their investigation requires novel approaches. Given the many contributors to obesity (weight gain, weight loss, weight maintenance, variability in body composition), as well as the dynamic nature of this issue, genomic tools must continue to be employed to evaluate all dimensions of the obesity phenotype, such as biochemical characteristics, susceptibility markers, nutrient intake, feeding practices and gene-environment interactions. Fundamental knowledge of the types of genes involved and available gene-diet interaction studies in children's obesity are reviewed. Although there is a paucity of existing literature in this specific domain of childhood obesity, ongoing investigations utilizing large cohorts have potential for providing the knowledge needed for targeted interventions in the future.

How much may I eat? Calorie estimates based upon energy expenditure prediction equations

How much may I eat? Most healthcare workers, when asked this question, have insufficient knowledge to educate their patients on a healthy energy intake level. In this review we examine the available methods for estimating adult energy requirements with a focus on the newly developed National Academy of Sciences/Institute of Medicine (NAS/IOM) doubly-labelled water total energy expenditure (TEE) prediction equations. An overview is first provided of the traditional factorial method of estimating energy requirements. We then extend this overview by exploring the development of the NAS/IOM TEE prediction models and their role in estimating energy requirements as a function of sex, age, weight, height and physical activity level. The NAS/IOM prediction models were developed for evaluating group energy requirements, although the formulas can be applied in individual 'example' patients for educational purposes. Potential limitations and interpretation issues of both the factorial and NAS/IOM methods are examined. This information should provide healthcare professionals with the tools and understanding to appropriately answer the question, 'How much may I eat?'

Influence of lipoprotein lipase gene Ser447Stop and β1-adrenergic receptor gene Arg389Gly polymorphisms and their interaction on obesity from childhood to adulthood: the Bogalusa Heart Study

OBJECTIVE

To investigate the influence of lipoprotein lipase (LPL) Ser447Stop and beta1-adrenergic receptor (ADRB1) Arg389Gly gene polymorphisms, individually and in combination, on obesity from childhood to adulthood.

DESIGN AND SUBJECTS

A community-based cohort of 1331 subjects (30% black and 70% white subjects) was followed over an average period of 23 years from childhood (age range: 4-17 years) to adulthood (age range:18-44 years).

MEASUREMENT

Body mass index (BMI, kg/m2) and LPL Ser447Stop and the ADRB1 Arg389Gly genotypes.

RESULTS

The frequency of the ADRB1 Gly389 allele was 0.25 in white subjects vs 0.39 in black subjects (P < 0.001); 0.08 vs 0.05 (P = 0.280) for the LPL Stop447 allele. There was no association between the LPL Stop447 allele and BMI among white and black subjects either in childhood and adulthood levels or annual change from childhood to adulthood. The ADRB1 Gly389 allele was associated with lower BMI only in black adults (P = 0.017). Further, the interaction effect of the LPL Stop447 allele and ADRB1 Gly389 allele on adult BMI or its annual change was significant in white subjects and in the total sample (P = 0.03-0.006). Childhood values tended to show a similar trend. Having both ADRB1 Gly389 allele and LPL Stop447 allele was associated with 71% (95% confidence interval: 26-89%) less odds for developing obesity from childhood to adulthood after adjusting for age, race, sex, and childhood BMI.

CONCLUSION

While Gly389 allele of the ADRB1 gene lowers obesity in black subjects, this allele in conjunction with Stop447 allele of the LPL gene lowers obesity in adults and attenuates the development of obesity from childhood to adulthood. These findings underscore the importance of gene-gene interaction in the assessment of genetic influences on complex traits such as obesity.

Science-Based Solutions to Obesity: What are the Roles of Academia, Government, Industry, and Health Care? Proceedings of a symposium, Boston, Massachusetts, USA, March 10-11, 2004 and Anaheim, California, USA, October 2, 2004

The complexity of the obesity epidemic requires the cooperation of key stakeholders in this effort. No one sector, academia, government, industry, or health care, has been successful in combating this disease to date. On March 10-11, 2004, The Harvard Medical School Division of Nutrition hosted the symposium "Science-Based Solutions to Obesity: What is the Role of Academia, Government, Industry, and Health care?" as a platform to address the role of these stakeholders, both individually and collectively, in combating the nation's epidemic of obesity. The proceedings from the symposium, included in this supplement, discuss the following: the science of obesity-related topics such as genetics, protein and weight loss, portion size, energy density, and behavior; the need for more aggressive government policies; industry's role in using research and development capabilities to promote healthier, portion-controlled products; and how to translate nutrition information from medical doctors to patients.

Gene-diet interaction in relation to the prevention of obesity and type 2 diabetes: evidence from the Finnish Diabetes Prevention Study

Both genetic and environmental factors are involved in the pathogenesis of obesity and type 2 diabetes. Most of the genetic studies on common obesity are confined to the links between a given gene polymorphism or gene loci and different phenotypes of obesity or anthropometric measures. Some studies indicate that genetic factors modify the weight reduction response to energy restriction or weight gain in the long-term. Only a few studies have focused on gene-diet interaction in the development of type 2 diabetes. The Finnish Diabetes Prevention Study shows (DPS) that the success of a lifestyle intervention depends also on the polymorphisms of those genes, which are suggested to play a role in energy metabolism, lipid metabolism, insulin resistance or insulin secretion. This review deals with selected genes examined so far in the DPS.

Expanding the Limits of Treatment—New Strategic Initiatives

The perception that weight reduction is rarely successful is, in fact, a misperception. Between 1999-2000 and 2001-2002, there were no significant changes among adults in the prevalence of overweight, obesity, or extreme obesity, or among children aged 6 through 19 years in the prevalence of at risk for overweight. The National Heart, Lung, and Blood Institute defines successful long-term weight loss as an intentional reduction of 10% from baseline maintained for 1 year. Modest weight loss is not only beneficial but also achievable for persons with overweight and obesity. Of the Americans who have tried to lose weight, almost 50% have maintained their weight loss successfully for at least 1 year. The remaining half, those who seem unable to prevent or reverse their obesity, challenge dietetics professionals to mobilize resources, confront issues at the heart of the obesity epidemic, and develop new solutions. Work to date has paid off for millions of persons. We have stopped the epidemic of obesity. Now it is time to do more by joining health care practitioners with all other stakeholders in the effort to prevent and reverse it.