Dietary energy density affects fat mass in early adolescence and is not modified by FTO variants

The association of dietary energy density and the risk of obesity, type 2 diabetes and metabolic syndrome: A systematic review and meta-analysis of observational studies

OBJECTIVES

There is a growing body of evidence linking dietary energy density (DED) with metabolic disorders like obesity, type 2 diabetes (T2D) and metabolic syndrome (MetS). However, according to our knowledge, there has been no systematic review and mate-analysis on T2D and MetS with DED. Therefore, this study aimed to investigate the association between DED with the risk of obesity, T2D and MetS in a systematic review and meta-analysis of observational studies.

METHODS

We searched all published studies according to the defined keywords up to march 2020 in the PubMed/Medline and Scopus databases. We excluded those that did not calculate DED for total intake, no observed association between obesity, T2D, MetS as the primary or one of the outcomes with DED, no reported odds ratio (OR), relative risk (RR) or hazard ratio (HR) estimates with 95% confidence intervals (CIs), studies in children under 2 years old, patients with cancer and pregnant women.

RESULTS

From 2282, after deleting the duplicates and irrelevant studies, we entered 58 articles ( 47 systematic reviews and 11 meta-analyse). We indicated an increased risk of T2D in relation to DED (OR: 1.25, 95% CI: 1.18-1.33, P < .001). But studies reviewed were inconsistent. All studies which examined the relationship between DED and MetS showed a positive relationship with an increased significant risk (OR: 1.59, 95% CI: 1.22-2.07, P < .001). Most articles reported a direct association between DED and obesity but the relationship between DED and risk of obesity was not significant (OR: 1.04, 95% CI: 0.92-1.17, P = .543).

CONCLUSION

In this systematic review and meta-analysis of observational studies, we found that the DED increased the risk of T2D and MetS but was not significant with the risk of obesity.

Baltic Adolescents' Health Behaviour: An International Comparison

The aim of the study is to assess the time trends in Baltic adolescents’ physical activity, dietary habits and BMI and compare the results with the average of the Health Behaviour in School-aged Children (HBSC) study. The research used HBSC data from 2006 to 2018. The total number of respondents was 17,458 in Estonia, 18,416 in Latvia and 20,466 in Lithuania. A logistic regression analysis was applied to estimate time trends in health behaviour indicators. The results demonstrated that Baltic adolescents’ physical activity has declined over the study years, except for Lithuanian girls. The prevalence of overweight adolescents has significantly increased since 2006. Dietary habits improved in all three Baltic countries, as consumption of vegetables increased, and soft drink consumption decreased during this time period. This research shows that a nationwide, highly representative study with health behaviour indicators enables us to assess regional differences compared to the HBSC average. The prevalence of overweight and obese adolescents in the Baltic countries has increased and moved closer to the HBSC average. Although Baltic adolescents’ daily vegetable consumption has increased over the last decade, it is still lower than the HBSC average.

Dietary Energy Density is Associated with Body Mass Index and Fat Mass in Early Adulthood

A cross-sectional study was conducted to investigate the association between body composition parameters as well as body mass index (BMI), and dietary energy density in a population of 538 young adults. Fat mass, fat mass percent, fat-free mass, and visceral fat were measured using a body composition analyzer. Daily energy intake was assessed using a 72-hr diet recall, and dietary energy density was calculated. Significant differences in dietary energy density among underweight, normal-weight and overweight/obesity young adults were identified (M = 1.42, SD = 0.26 vs. M = 1.52, SD = 0.46 vs. M = 1.66, SD = 0.53, p = .002). Dietary energy density was associated with BMI (β = .961; CI 95% = 0.335, 1.586; p = .0030), fat mass percent (β = 1.921; CI 95% = 0.707, 3.135; p = .002), and fat mass (β = 2.146; CI 95% = 0.827, 3.466; p = .001). Dietary energy density might be considered as an important aspect in the obesity nutritional education programs in young people.

Dietary energy density is associated with body mass index-for-age in Mexican adolescents

Dietary energy density (DED) has been widely considered a risk factor for weight gain. In adolescents, however, the evidence is inconclusive, and in Mexico, the ways in which DED is associated with overweight and obesity are unknown. Our study analysed the association of DED with overweight or obesity (OW-O) in Mexican adolescents included in the National Health and Nutrition Survey 2012 (ENSANUT 2012). We analysed the data from a 7-day Food Frequency Questionnaire administered to 2,203 Mexican adolescents aged 12-19 years. DED was calculated excluding all beverages. Plausible and implausible reporters were identified based on the relationship between the reported energy intake and the estimated energy requirement. The association of DED with body mass index (BMI)-for-age and OW-O was analysed using multivariate statistical models restricted to plausible reporters. The combined prevalence of overweight and obesity was 35.4% in the complete sample and 27.8% in the sample of plausible reporters. Mean DED was 177 kcal/100 g, with higher DED in the north of the country. The proportion of plausible reporters was 38.5%. We found a positive association between high DED and the BMI-for-age z-score (β = 0.347; 95% CI [0.101, 0.594]; P = 0.006), controlling for sociodemographic and dietary variables, but no significant association with OW-O. It is necessary to consider the DED in the design and implementation of strategies to reduce energy density in the diets of young Mexicans.

Associations of dietary energy density with body composition and cardiometabolic risk in children with overweight and obesity: role of energy density calculations, under-reporting energy intake and physical activity

This study examined (1) the association of dietary energy density from solid (EDS) and solid plus liquids (EDSL) with adiposity and cardiometabolic risk factors (CRF) in children with overweight and obesity, (2) the effect of under-reporting on the mentioned associations and (3) whether the association between ED and body composition and CRF is influenced by levels of physical activity. In a cross-sectional design, 208 overweight and obese children (8–12-year-old; 111 boys) completed two non-consecutive 24 h recalls. ED was calculated using two different approaches: EDS and EDSL. Under-reporters were determined with the Goldberg method. Body composition, anthropometry and fasting blood sample measurements were performed. Moderate to vigorous physical activity (MVPA) was registered with accelerometers (7-d-register). Linear regressions were performed to evaluate the association of ED with the previously mentioned variables. Neither EDS nor EDSL were associated with body composition or CRF. However, when under-reporters were excluded, EDS was positively associated with BMI (P=0·019), body fat percentage (P=0·005), abdominal fat (P=0·008) and fat mass index (P=0·018), while EDSL was positively associated with body fat percentage (P=0·008) and fat mass index (P=0·026). When stratifying the group according to physical activity recommendations, the aforementioned associations were only maintained for non-compliers. Cluster analysis showed that the low-ED and high-MVPA group presented the healthiest profile for all adiposity and CRF. These findings could partly explain inconsistencies in literature, as we found that different ED calculations entail distinct results. Physical activity levels and excluding under-reporters greatly influence the associations between ED and adiposity in children with overweight and obesity.

Aetiology of eating behaviours: A possible mechanism to understand obesity development in early childhood

Childhood obesity is an issue of public health concern that is understood to emerge due to disequilibrium in energy homeostasis. This commentary explores literature regarding neuro-biological mechanisms of energy homeostasis and the relationship between subjective measures of children's eating behaviours and objective measures of appetite, in order to better understand the aetiology of childhood obesity. Early life influences, such as in utero exposure, breastfeeding, and general disadvantage, appear to have an important influence on neuro-biological mechanisms of appetite and may contribute to inequitable distributions of obesity within the population. Subject measures of eating behaviours appear to capture various aspects of neuro-biologically driven (objective) appetite systems, however, these systems are complex, interdependent and not yet fully understood. Future research focusing attention on early life influences on appetite and eating behaviours is warranted to increase understanding of differences in rates of obesity within the population, to determine opportunities for targeted obesity prevention initiatives, and to explore the potential to measure change in eating behaviours as a marker of appetite and obesity risk.

Dietary Energy Density and Its Association with Overweight or Obesity in Adolescents: A Systematic Review of Observational Studies

Dietary energy density (DED) has been identified as a crucial dietary factor in body weight control, in that higher DED has been associated with weight gain. To our knowledge, no review studies have explained this association specifically in adolescents. The aim of this study was to describe the association of DED with overweight or obesity (OW/O) in adolescents, as derived from observational studies. We conducted a systematic search of the MEDLINE/PubMed and Science Direct databases, including studies published between January 2000 and December 2017. We selected the studies that included adolescents (aged 10⁻19 years) and contained DED-related information and anthropometric measurements of OW/O. From 1149 candidate studies, 30 were selected, though only 12 met all the inclusion criteria. Of these, only four found a positive association between DED and certain OW/O indicators, six found no association and two showed an inverse association with weight gain. These studies differed in several aspects such as design, DED calculation method and dietary assessment tool, leading to inconsistent results. Methodological differences found among the examined studies did not allow us to establish a clear conclusion of this association. Evidence in adolescents was also poor. New, standardized methodological approaches should be considered in future studies.

Genetics of fat intake in the determination of body mass

Body mass and fat intake are multifactorial traits that have genetic and environmental components. The gene with the greatest effect on body mass is FTO (fat mass and obesity-associated), but several studies have shown that the effect of FTO (and of other genes) on body mass can be modified by the intake of nutrients. The so-called gene–environment interactions may also be important for the effectiveness of weight-loss strategies. Food choices, and thus fat intake, depend to some extent on individual preferences. The most important biological component of food preference is taste, and the role of fat sensitivity in fat intake has recently been pointed out. Relatively few studies have analysed the genetic components of fat intake or fatty acid sensitivity in terms of their relation to obesity. It has been proposed that decreased oral fatty acid sensitivity leads to increased fat intake and thus increased body mass. One of the genes that affect fatty acid sensitivity is CD36 (cluster of differentiation 36). However, little is known so far about the genetic component of fat sensing. We performed a literature review to identify the state of knowledge regarding the genetics of fat intake and its relation to body-mass determination, and to identify the priorities for further investigations.

Dietary fat intake modifies the influence of the FTO rs9939609 polymorphism on adiposity in adolescents: The HELENA cross-sectional study

BACKGROUND AND AIMS

The fat mass and obesity associated gene (FTO) has been associated with obesity and dietary intake. The aims were: (i) To assess whether energy and macronutrient intakes were different across the FTOrs9939609 genotypes in adolescents, and (ii) to explore whether dietary fat intake modified the association of the rs9939609 polymorphism with adiposity.

METHODS AND RESULTS

The FTOrs9939609 polymorphism was genotyped in 652 adolescents (53% females, 14.8 ± 1.2 years, TT = 246, TA = 296, AA = 110). Energy and macronutrient intake were assessed by two non-consecutive 24 h-recalls. Weight, height, waist circumference and skinfold thicknesses were measured and body fat percent was calculated. Energy and macronutrient intake were similar across the FTOrs9939609 genotypes (P > 0.2). There were significant interactions between the FTO polymorphism and fat intake on adiposity estimates (P < 0.05). In adolescents whose fat intake was below 30% (N = 203), the A allele of rs9939609 was not associated with adiposity indices. In contrast, in adolescents whose fat intake was between 30% and 35% of energy (N = 190), the rs9939609 polymorphism was associated with a 1.9% higher body fat per risk allele (95%CI: 0.39, 3.33; P < 0.05), and in those whose fat intake was higher than 35% (N = 259), it was associated with a 2.8% higher body fat per risk allele (95%CI: 1.27, 4.43; P < 0.001).

CONCLUSIONS

These findings support the concept that the deleterious effect of the FTOrs9939609 polymorphism on adiposity is exacerbated in adolescents consuming high fat diets. In contrast, the consumption of low fat diets (<30% of energy) may attenuate the genetic predisposition to obesity in risk allele carriers.

Association between energy density and diet cost in children

Highlights

The average of the energy-adjusted diet cost in 6-12 years-old children was 2.17€/1000Kcal (SD + 0.49).Energy-density diets (EDs - Kcal/g) were calculated by three distinct methods: (1) with food and all beverages (ED1), (2) with food and caloric beverages (ED2), and (3) only with food (ED3).The distributions of the three EDs were statistically different, being higher the ED3 - calculated excluding all beverages (1.15Kcal (SD + 0.28) vs. ED2: 1.10Kcal/g; SD + 0.24 vs. ED1: 0.99Kcal/g; SD + 0.22).Lower energy-density diets (EDs) were associated with higher diet cost in a sample of school children from a Mediterranean country, regardless the differences between the EDs calculated by three distinct methods.

Background

Lower energy density diets tend to cost more, but data using different ways to calculate the dietary energy density, is scarce.

Objectives

To estimate the dietary energy density, and to assess how it is associated with the diet cost in children.

Methods

Data were obtained from a community-based survey from public elementary schools in Portugal. Dietary intake of 464 children (6-12 years) was assessed by a 24 h recall in 2007/2008. Dietary energy density (kcal/g) was calculated as following: (1) with food and all beverages (ED1), (2) with food and caloric beverages (ED2), and (3) only with food (ED3). Energy-adjusted diet cost (€/1000 kcal) was calculated based on the collection of food prices from a national leader supermarket. Anthropometric measures were taken and socio-demographic data were obtained from parents. Logistic regression was used to estimate the association between diet cost and energy density.

Results

For boys, the energy-adjusted diet cost of the highest third of energy density was lower, between 81% in the ED3 (p for trend <0.001) and 87% in the ED1 (p for trend <0.001), compared to the lowest third. Girls showed similar, but weaker associations.

Conclusions

Higher dietary energy density was associated with lower dietary cost among children.

The independent prospective associations of activity intensity and dietary energy density with adiposity in young adolescents

There is limited evidence on the prospective association of time spent in activity intensity (sedentary (SED), moderate (MPA) or vigorous (VPA) physical activity) and dietary intake with adiposity indicators in young people. This study aimed to assess associations between (1) baseline objectively measured activity intensity, dietary energy density (DED) and 4-year change in adiposity and (2) 4-year change in activity intensity/DED and adiposity at follow-up. We conducted cohort analyses including 367 participants (10 years at baseline, 14 years at follow-up) with valid data for objectively measured activity (Actigraph), DED (4-d food diary), anthropometry (waist circumference (WC), %body fat (%BF), fat mass index (FMI), weight status) and covariates. Linear and logistic regression models were fit, including adjustment for DED and moderate-to-vigorous physical activity. Results showed that baseline DED was associated with change in WC (β for 1kJ/g difference: 0·71; 95% CI 0·26, 1·17), particularly in boys (1·26; 95% CI 0·41, 2·16 v. girls: 0·26; 95% CI −0·34, 0·87), but not with %BF, FMI or weight status. In contrast, baseline SED, MPA or VPA were not associated with any of the outcomes. Change in DED was negatively associated with FMI (β for 1kJ/g increase: −0·86; 95% CI −1·59, −0·12) and %BF (−0·86; 95% CI −1·25, −0·11) but not WC (−0·27; 95% CI −1·02, 0·48). Change in SED, MPA and VPA did not predict adiposity at follow-up. In conclusion, activity intensity was not prospectively associated with adiposity, whereas the directions of associations with DED were inconsistent. To inform public health efforts, future studies should continue to analyse longitudinal data to further understand the independent role of different energy-balance behaviours in changes in adiposity in early adolescence.

Diet, growth, and obesity development throughout childhood in the Avon Longitudinal Study of Parents and Children

Publications from the Avon Longitudinal Study of Parents and Children covering diet, growth, and obesity development during childhood are reviewed. Diet was assessed by food frequency questionnaires and food records. Growth data were collected by routine measurements, and in standardized clinics, body fatness was assessed by bioelectrical impedance and DXA (dual-energy X-ray absorptiometry) scans. Diets changed dramatically during the preschool period with an increase in the intake of free (added) sugars (12.3% rising to 16.4% of energy) that remained similar until adolescence. This was due to increased intake of energy-dense, nutrient-poor foods. Two periods of rapid growth were identified; infancy and mid-childhood (ages 7-11 y) and both were associated with obesity development. Diets with high energy density were associated with increasing fat mass from mid-childhood until adolescence. Genetic and dietary factors showed independent associations with increasing adiposity. At all ages studied, there were dietary inequalities related to maternal educational attainment that may influence inequalities found in obesity development. The Avon Longitudinal Study of Parents and Children has provided valuable insights into how disparities in diet and growth may affect the development of ill health in adulthood.

The Cross-Sectional Association of Energy Intake and Dietary Energy Density with Body Composition of Children in Southwest China

OBJECTIVE

We examined whether dietary energy intake (EI) and dietary energy density (ED) were cross-sectionally associated with body composition of children living in Southwest China.

DESIGN AND METHODS

Multivariate regression analyses were performed on three day, 24 h dietary recall data and information on potential confounders from 1207 participants aged 8-14 years. EI was calculated from all foods and drinks and ED was classified into five categories. Body mass index (BMI) z-scores, percentage of body fat (%BF), fat mass index (FMI), fat-free mass index (FFMI) and ratio of waist to hip circumference (WHR) were used to describe body composition.

RESULTS

Boys with higher total EI had higher BMI z-scores, %BF, and FMI than boys with lower total EI both before and after measurements were adjusted for confounders (age, fiber intake, physical activity, the timing of adding complementary foods, paternal education level and maternal BMI) (p ≤ 0.04). However, EI was not associated with body composition in girls. Dietary ED, in any category, was not associated with body composition in either gender.

CONCLUSIONS

Dietary ED was not associated with body composition of children in Southwest China, while dietary EI in boys, not girls, was positively associated with body composition. Reducing dietary energy intake may help to prevent obesity and related diseases in later life among boys living in Southwest China.

The 'Fat Mass and Obesity Related' (FTO) gene: Mechanisms of Impact on Obesity and Energy Balance

A cluster of single nucleotide polymorphisms (SNPs) in the first intron of the fat mass and obesity related (FTO) gene were the first common variants discovered to be associated with body mass index and body fatness. This review summarises what has been later discovered about the biology of FTO drawing together information from both human and animal studies. Subsequent work showed that the 'at risk' alleles of these SNPs are associated with greater food intake and increased hunger/lowered satiety, but are not associated with altered resting energy expenditure or low physical activity in humans. FTO is an FE (II) and 2-oxoglutarate dependent DNA/RNA methylase. Contrasting the impact of the SNPs on energy balance in humans, knocking out or reducing activity of the Fto gene in the mouse resulted in lowered adiposity, elevated energy expenditure with no impact on food intake (but the impact on expenditure is disputed). In contrast, overexpression of the gene in mice led to elevated food intake and adiposity, with no impact on expenditure. In rodents, the Fto gene is widely expressed in the brain including hypothalamic nuclei linked to food intake regulation. Since its activity is 2-oxoglutarate dependent it could potentially act as a sensor of citrate acid cycle flux, but this function has been dismissed, and instead it has been suggested to be much more likely to act as an amino acid sensor, linking circulating AAs to the mammalian target of rapamycin complex 1. This may be fundamental to its role in development but the link to obesity is less clear. It has been recently suggested that although the obesity related SNPs reside in the first intron of FTO, they may not only impact FTO but mediate their obesity effects via nearby genes (notably RPGRIP1L and IRX3).

Variability in children's eating response to portion size. A biobehavioral perspective

The portion size of foods and beverages offered at meals has been shown to significantly affect human food intake. While portion size effects appear to be fairly robust across studies in adults, findings from studies in children are generally more variable and do not reliably predict a significant portion size effect. Eating behaviors are still forming at a young age and individual differences in children's response to portion size will depend upon genetic predisposition interacting with the child's environment. The aim of this review is to present and discuss evidence that innate controls of appetite and eating, which involve genes that encode key hormones and neuropeptides implicated in processes of satiety and satiation, may differentially affect meal size. We also present evidence that children's response to portion size is learned and this is in turn shaped by upbringing, the early family and home environment. The review will conclude with a conceptual model that illustrates how biological and environmental factors may interact to shape child eating traits including a behavioral susceptibility to overeating when large portion sizes are available.

The effects of genetic variation in FTO rs9939609 on obesity and dietary preferences in Chinese Han children and adolescents

The association of the rs9939609 single nucleotide polymorphism in FTO gene with obesity has been extensively investigated in studies of populations of European, African, and Asian ancestry. However, inconsistent results have been reported in Asian populations, and the relationship of FTO variation and dietary behaviors has only rarely been examined in Chinese children and adolescents. The aim of this study was to assess the association of rs9939609 with obesity and dietary preferences in childhood in a Chinese population. Epidemiological data including dietary preferences were collected in interviews using survey questionnaires, and rs9939609 genotype was determined by real-time PCR. The associations of rs9939609 genotypes with obesity and dietary preferences were analyzed by multivariate logistic regression using both additive and dominant models. The results showed that subjects with a TA or AA genotype had an increased risk of obesity compared with the TT participants; the odds ratios (ORs) were 1.47 (95% CI: 1.25–1.71, P = 1.73×10⁻⁶), and 3.32 (95% CI: 2.01–5.47, P = 2.68×10⁻⁶), respectively. After adjusting for age and gender, body mass index, waist circumference, hip circumference, systolic blood pressure, diastolic blood pressure, fasting blood glucose, triglycerides, and low-density lipoprotein cholesterol were higher, and high-density lipoprotein cholesterol was lower in TA and AA participants than in those with the TT genotype. After additionally controlling for body mass index, the association remained significant only for systolic blood pressure (P = 0.005). Compared with TT participants, those with the AA genotype were more likely to prefer a meat-based diet (OR = 2.81, 95% CI: 1.52–5.21). The combined OR for obesity in participants with TA/AA genotypes and preference for a meat-based diet was 4.04 (95% CI: 2.8–5.81) compared with the TT participants who preferred a plant-based diet. These findings indicate the genetic variation of rs9939609 is associated with obesity and dietary preferences in Chinese children and adolescents.

Influencing and modifying children's energy intake: the role of portion size and energy density

Childhood obesity is of concern worldwide. The portion size (PS) and energy density (ED) of food are two major determinants of children's energy intake (EI). Trends towards increasing PS are most apparent and best documented in the USA, where PS of numerous food products have increased in the marketplace over the past three decades, particularly high-energy dense foods. Analyses of population-level dietary surveys have confirmed this trend in children for both in- and out-of-home eating, and a plethora of observational evidence positively associates PS, ED and adiposity in children. A limited number of intervention studies provide clear evidence that children, even as young as 2 years, respond acutely to increasing PS, with some studies also demonstrating the additive effects of increased ED in promoting excessive EI. However, most of the evidence is based on children aged 3-6 years and there is a paucity of data in older children and adolescents. It is unclear whether decreasing PS can have the opposite effect on children's EI but recent acute studies have demonstrated that the incorporation of lower energy dense foods, such as fruit and vegetables, into children's meals down-regulates EI. Although a direct causal link between PS and obesity remains to be established, the regular consumption of larger PS of energy dense foods do favour obesity-promoting eating behaviours in children. Further research is required to establish the most feasible and effective interventions and policies to counteract the deleterious impact of PS and ED on children's EI.

Programming effects of FTO in the development of obesity

It is becoming increasingly recognized that early-life nutritional, metabolic and environmental factors can have a long-term impact on the early onset of obesity, type 2 diabetes and cardiovascular diseases. Numerous experimental and epidemiological observations support the concept that an individual's response to their adult lifestyle and nutritional environment depends not only on their genetic susceptibility but also on their previous early-life experiences. The current research challenge is to determine the primary pathways contributing to 'non- or epi-genetic' causes of excess adult weight gain and adiposity. Evidence from the fields of genetic epidemiology, life course modelling and diet-induced foetal programming all support a role for the FTO gene in this complex biological interaction. It may provide a missing link in the developmental regulation of energy metabolism. Our review therefore considers the role of the FTO gene in the early-life determination of body weight, body composition and energy balance. We will summarize current knowledge on FTO biology combining human genetic epidemiology, molecular models and findings from animal studies. Notably, we will focus on the role of FTO in energy balance in humans, the importance of FTO polymorphisms in childhood growth and the impact of foetal nutrition. Ultimately, we propose a new hypothesis for future research designed to understand the role of FTO in setting gene expression in metabolically active tissues.

Childhood obesity prevention from cell to society

Nearly 40% of US children are overweight or obese. We propose that a cell-to-society integrative approach is needed that takes into account biology, early child development, home and childcare environments, and public policy. This approach requires researchers, families, and policy makers to work together to develop preventative strategies and interventions that benefit the nutrition and wellbeing of young children and their families, and ultimately the health of the nation.

Obesity-susceptibility loci and the tails of the pediatric BMI distribution

OBJECTIVE

To determine whether previously identified adult obesity susceptibility loci were associated uniformly with childhood BMI across the BMI distribution.

DESIGN AND METHODS

Children were recruited through the Children's Hospital of Philadelphia (n = 7,225). Associations between the following loci and BMI were assessed using quantile regression: FTO (rs3751812), MC4R (rs12970134), TMEM18 (rs2867125), BDNF (rs6265), TNNI3K (rs1514175), NRXN3 (rs10146997), SEC16B (rs10913469), and GNPDA2 (rs13130484). BMI z-score (age and gender adjusted) was modeled as the dependent variable, and genotype risk score (sum of risk alleles carried at the 8 loci) was modeled as the independent variable.

RESULTS

Each additional increase in genotype risk score was associated with an increase in BMI z-score at the 5th, 15th, 25th, 50th, 75th, 85th, and 95th BMI z-score percentiles by 0.04 (±0.02, P = 0.08), 0.07 (±0.01, P = 9.58 × 10(-7) ), 0.07 (±0.01, P = 1.10 × 10(-8) ), 0.09 (±0.01, P = 3.13 × 10(-22) ), 0.11 (±0.01, P = 1.35 × 10(-25) ), 0.11 (±0.01, P = 1.98 × 10(-20) ), and 0.06 (±0.01, P = 2.44 × 10(-6) ), respectively. Each additional increase in genotype risk score was associated with an increase in mean BMI z-score by 0.08 (±0.01, P = 4.27 × 10(-20) ).

CONCLUSION

Obesity risk alleles were more strongly associated with increases in BMI z-score at the upper tail compared to the lower tail of the distribution.

Significant genotype by diet (G × D) interaction effects on cardiometabolic responses to a pedigree-wide, dietary challenge in vervet monkeys (Chlorocebus aethiops sabaeus)

Nutrient composition of a diet (D) has been shown to interact with genetic predispositions (G) to affect various lipid phenotypes. Our aim in this study was to confirm G × D interaction and determine whether the interaction extends to other cardiometabolic risk factors such as glycemic measures and body weight. Subjects were vervet monkeys (Chlorocebus aethiops sabaeus; n = 309) from a multigenerational pedigreed colony initially fed with a plant-based diet, standard primate diet (18% calories from protein, 13% from fat, and 69% from carbohydrates), and subsequently challenged for 8 weeks with a diet modeled on the typical American diet (18% calories from protein, 35% from fat, and 47% from carbohydrates). Our results showed that although exposure to the challenge diet did not result in significant changes in weight, most lipid and glycemic biomarkers moved in an adverse direction (P < 0.01). Quantitative genetic analyses showed that cardiometabolic phenotypes were significantly heritable under both dietary conditions (P < 0.05), and there was significant evidence of G × D interaction for these phenotypes. We observed significant differences in the additive genetic variances for most lipid phenotypes (P < 10(-4) ), indicating that the magnitude of genetic effects varies by diet. Furthermore, genetic correlations between diets differed significantly from 1 with respect to insulin, body weight, and some lipid phenotypes (P < 0.01). This implied that distinct genetic effects are involved in the regulation of these phenotypes under the two dietary conditions. These G × D effects confirm and extend previous observations in baboons (Papio sp.) and suggest that mimicking the typical human nutritional environment can reveal genetic influences that might not be observed in animals consuming standard, plant-based diets.

Association Study of Fat-mass and Obesity-associated Gene and Body Mass Index in Japanese Patients with Schizophrenia and Healthy Subjects

OBJECTIVE

Fat-mass and obesity-associated (FTO) gene is known to be involved in the pathophysiology of obesity and a single-nucleotide polymorphism (SNP) rs9939609 of FTO gene is repeatedly confirmed to be associated with body mass index (BMI) and obesity. The aim of this study is to elucidate effects of FTO gene polymorphism on BMI in Japanese patients with schizophrenia and healthy subjects.

METHODS

Three hundred fifty one patients with schizophrenia and 342 age- and sex-matched healthy subjects participated in the study. Information on BMI and antipsychotic medication was also collected from patients and healthy subjects. Genotype of the FTO SNP rs9939609 was determined by TaqMan SNP Genotyping Assays.

RESULTS

There was no significant difference in BMI between patients and healthy subjects. No significant difference in BMI was observed among any medications. We observed no significant difference in rs9939609 allele frequencies between patients and healthy subjects. There was a significant difference in BMI between healthy subjects with risk (AA or TA) genotypes and those with TT genotype. We also observed a significant positive correlation between the number of risk allele (A allele) and BMI in healthy subjects.

CONCLUSION

Our study suggested that FTO rs9939609 polymorphism might have some impacts on the BMI in healthy subjects, but might not have same impacts on the BMI of patients with schizophrenia.

The impact of intronic single nucleotide polymorphisms and ethnic diversity for studies on the obesity gene FTO

In 2007, the first common genetic variants were identified, which undoubtedly affect our susceptibility to obesity. These variants are located in the fat mass and obesity-associated gene FTO. Since then, over 50 loci for common obesity have been identified. As the research on these loci is still at an early stage, there is a great need to review, for clarification purposes, the current research on FTO, as this is likely to influence future studies. Based on the current knowledge, FTO seems to be directly involved in the regulation of energy intake, but there is an urgent need for the identification of regulatory polymorphisms. Thus, herein, we discuss current knowledge and highlight putative functional regions in FTO based on published data and computer-based analysis.

Genetics of pediatric obesity

Onset of obesity has been anticipated at earlier ages, and prevalence has dramatically increased worldwide over the past decades. Epidemic obesity is mainly attributable to modern lifestyle, but family studies prove the significant role of genes in the individual's predisposition to obesity. Advances in genotyping technologies have raised great hope and expectations that genetic testing will pave the way to personalized medicine and that complex traits such as obesity will be prevented even before birth. In the presence of the pressing offer of direct-to-consumer genetic testing services from private companies to estimate the individual's risk for complex phenotypes including obesity, the present review offers pediatricians an update of the state of the art on genomics obesity in childhood. Discrepancies with respect to genomics of adult obesity are discussed. After an appraisal of findings from genome-wide association studies in pediatric populations, the rare variant-common disease hypothesis, the theoretical soil for next-generation sequencing techniques, is discussed as opposite to the common disease-common variant hypothesis. Next-generation sequencing techniques are expected to fill the gap of "missing heritability" of obesity, identifying rare variants associated with the trait and clarifying the role of epigenetics in its heritability. Pediatric obesity emerges as a complex phenotype, modulated by unique gene-environment interactions that occur in periods of life and are "permissive" for the programming of adult obesity. With the advent of next-generation sequencing techniques and advances in the field of exposomics, sensitive and specific tools to predict the obesity risk as early as possible are the challenge for the next decade.

Dietary energy density and body weight in adults and children: a systematic review

Energy density is a relatively new concept that has been identified as an important factor in body weight control in adults and in children and adolescents. The Dietary Guidelines for Americans 2010 encourages consumption of an eating pattern low in energy density to manage body weight. This article describes the systematic evidence-based review conducted by the 2010 Dietary Guidelines Advisory Committee (DGAC), with support from the US Department of Agriculture's Nutrition Evidence Library, which resulted in this recommendation. An update to the committee's review was prepared for this article. PubMed was searched for English-language publications from January 1980 to May 2011. The literature review included 17 studies (seven randomized controlled trials, one nonrandomized controlled trial, and nine cohort studies) in adults and six cohort studies in children and adolescents. Based on this evidence, the 2010 Dietary Guidelines Advisory Committee concluded that strong and consistent evidence in adults indicates that dietary patterns relatively low in energy density improve weight loss and weight maintenance. In addition, the committee concluded that there was moderately strong evidence from methodologically rigorous longitudinal cohort studies in children and adolescents to suggest that there is a positive association between dietary energy density and increased adiposity. This review supports a relationship between energy density and body weight in adults and in children and adolescents such that consuming diets lower in energy density may be an effective strategy for managing body weight.

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.

Predictors of measurement error in energy intake during pregnancy

Nutrition plays a critical role in maternal and fetal health; however, research on error in the measurement of energy intake during pregnancy is limited. The authors analyzed data on 998 women living in central North Carolina with singleton pregnancies during 2001-2005. Second-trimester diet was assessed by food frequency questionnaire. Estimated energy requirements were calculated using Institute of Medicine prediction equations, with adjustment for energy costs during the second trimester. Implausible values for daily energy intake were determined using confidence limits of agreement for energy intake/estimated energy requirements. Prevalences of low energy reporting (LER) and high energy reporting (HER) were 32.8% and 12.9%, respectively. In a multivariable analysis, pregravid body mass index was related to both LER and HER; LER was higher in both overweight (odds ratio = 1.96, 95% confidence interval: 1.26, 3.02; P = 0.031) and obese (odds ratio = 3.29, 95% confidence interval: 2.33, 4.65; P < 0.001) women than in normal-weight counterparts. Other predictors of LER included marriage and higher levels of physical activity. HER was higher among subjects who were underweight, African-American, and less educated and subjects who had higher depressive symptom scores. LER and HER are prevalent during pregnancy. Identifying their predictors may improve data collection and analytic methods for reducing systematic bias in the study of diet and reproductive outcomes.

The genetic epidemiology of obesity: a case study

Obesity (OMIM #601665) is a disease where excessive stores of body fat impact negatively on health. The first law of thermodynamics dictates that energy cannot be created or destroyed so if energy is taken into the body, but not transformed to ATP for metabolic work or dissipated as heat, it will be stored as fat. Therefore, the ultimate cause of obesity is a long-term positive energy imbalance [energy intake (EI) exceeds energy expenditure (EE)]. Despite this simple explanation, there is no single reason why EI may exceed EE meaning that the proximate causes of obesity are multi-factorial in origin involving a complex interplay of genetic, behavioural, and environmental influences on metabolism, diet, and activity.

Evidences on three relevant obesogenes: MC4R, FTO and PPARγ. Approaches for personalized nutrition

Obesity is a complex disease that results from the interaction between lifestyle (dietary patterns and sedentary habits) and genetic factors. The recognition of a genetic basis for human obesity has driven to identify putative causal genes to understand the pathways that control body mass and fat deposition in humans as well as to provide personalized treatments and prevention strategies to fight against obesity. More than 120 candidate genes have been associated with obesity-related traits. Genome-wide association study has so far identified over 20 novel loci convincingly associated with adiposity. This review is specifically focused on the study of the effects of melanocortin 4 receptor, Peroxisome proliferator-activated receptor γ and fat mass and obesity associated (FTO) gene variants and their interactions with dietary intake, physical activity or drug administration on body weight control. The advances in this field are expected to open new ways in genome-customized diets for obesity prevention and therapy following personalized approaches.

FTO variant, energy intake, physical activity and basal metabolic rate in Caucasians. The HAPIEE study

The FTO gene variants are the most important genetic determinants of body weight and obesity known so far, but the mechanism of their effect remains unclear. We have analyzed FTO rs17817449 variant (G>T in first intron) in 6024 adults aged 45-69 years to assess the potential mediating role of diet and physical activity. Diet was assessed by a 140-item food frequency questionnaire. Physical activity was measured by hours spent during a typical week by sport, walking and other activities outside of work requiring heavy and medium physical activity. Basal metabolic rate was calculated according Schofield formula. The FTO variant was significantly associated with body mass index (means in GG, GT and TT carriers were 28.7, 28.2 and 27.8 kg/m(2), p<0.001) and basal metabolic rate (BMR) (means in GG, GT and TT were 1603, 1588 and 1576 kcal per day, respectively, p<0.008) but it was not associated with physical activity, total energy intake or with energy intakes from fat, carbohydrates, proteins or alcohol. Results were essentially similar in men and women and the adjustment for physical activity or dietary energy intake did not reduce the effect of the FTO polymorphism. Means of BMR per kg of body weight was lowest in GG carriers (20.09, 20.21 for GT and 20.30 for TT, p<0.006) and this effect was more pronounced in females. These results suggest that the effect of the FTO rs17817449 variant on BMI in Caucasian adults is not mediated by energy intake or physical activity, but some effect on BMR per kg of body weight is possible.

Life-course analysis of a fat mass and obesity-associated (FTO) gene variant and body mass index in the Northern Finland Birth Cohort 1966 using structural equation modeling

The association between variation in the fat mass and obesity-associated (FTO) gene and adulthood body mass index (BMI; weight (kg)/height (m)²) is well-replicated. More thorough analyses utilizing phenotypic data over the life course may deepen our understanding of the development of BMI and thus help in the prevention of obesity. The authors used a structural equation modeling approach to explore the network of variables associated with BMI from the prenatal period to age 31 years (1965–1997) in 4,435 subjects from the Northern Finland Birth Cohort 1966. The use of structural equation modeling permitted the easy inclusion of variables with missing values in the analyses without separate imputation steps, as well as differentiation between direct and indirect effects. There was an association between the FTO single nucleotide polymorphism rs9939609 and BMI at age 31 years that persisted after controlling for several relevant factors during the life course. The total effect of the FTO variant on adult BMI was mostly composed of the direct effect, but a notable part was also arising indirectly via its effects on earlier BMI development. In addition to well-established genetic determinants, many life-course factors such as physical activity, in spite of not showing mediation or interaction, had a strong independent effect on BMI.

The genetics of obesity: FTO leads the way

In 2007, an association of single nucleotide polymorphisms (SNPs) in the fat mass and obesity-associated (FTO) gene region with body mass index (BMI) and risk of obesity was identified in multiple populations, making FTO the first locus unequivocally associated with adiposity. At the time, FTO was a gene of unknown function and it was not known whether these SNPs exerted their effect on adiposity by affecting FTO or neighboring genes. Therefore, this breakthrough association inspired a wealth of in silico, in vitro, and in vivo analyses in model organisms and humans to improve knowledge of FTO function. These studies suggested that FTO plays a role in controlling feeding behavior and energy expenditure. Here, we review the approaches taken that provide a blueprint for the study of other obesity-associated genes in the hope that this strategy will result in increased understanding of the biological mechanisms underlying body weight regulation.

A FTO variant and risk of acute coronary syndrome

BACKGROUND

The FTO gene plays an important role in the determination of body weight and BMI and it has been suspected of being associated with all-case mortality.

METHODS

We have analyzed the FTO rs17817449 variant in consecutive 1092 male patients with acute coronary syndrome (ACS) and in 1191 randomly selected Caucasian individuals (population controls).

RESULTS

The FTO variant was significantly associated with BMI both in controls (P<0.02) and ACS patients (P<0.01). In both groups, BMI was highest in GG homozygotes and lowest in TT homozygotes. There was a significant difference between the ACS patients and controls in the frequency of the FTO genotype GG (21.4% vs. 15.9%, P<0.005). FTO GG homozygotes had a significantly increased risk of ACS, compared with TT homozygotes which was independent of age and BMI (odds ratio 1.49, 95% confidence interval 1.16-1.93). The odds ratio of ACS patients for the GG genotype remained significant even after the exclusion of diabetics (100 controls and 339 ACS patients), with OR 1.32 (95% CI 1.01-1.72).

CONCLUSIONS

This study provides an evidence of an association between the FTO variant and risk of ACS in Caucasian males.

A variant in the fat mass and obesity-associated gene (FTO) and variants near the melanocortin-4 receptor gene (MC4R) do not influence dietary intake

We investigated the role of the fat mass and obesity associated gene (FTO) and variants near the melanocortin-4 receptor gene (MC4R) in modulating habitual intake of total energy and macronutrients, glycemic index, glycemic load, dietary energy density, and energy from 20 food groups in adults. In a population-based sample of 756 healthy adult twin pairs, we studied associations between FTO rs9939609, near-MC4R rs12970134, rs17700633, and rs17782313 single nucleotide polymorphisms (SNP) and habitual dietary intake. Habitual dietary intake was assessed by a 247-question FFQ. Nontransformed variables and variables transformed by natural logarithm were analyzed by linear regression and dichotomized variables were analyzed by logistic regression. FTO SNP rs9939609 was not associated with habitual dietary intake. For the near-MC4R SNP rs12970134 and rs17700633, we found significant positive associations with intake of energy from whole grains (P >or= 0.04). These associations did not remain significant after controlling for multiple testing. The outcome of this study indicates that polymorphisms in the FTO gene and near the MC4R gene do not have a role in regulating food intake and preference for specific food items.

Survivors of acute lymphoblastic leukemia and body mass changes

IMPORTANCE OF THE FIELD

Obesity is a rapidly growing challenge that has now reached epidemic proportions. Along with malnutrition, it causes increasing morbidity and mortality in the general population. Survivors of pediatric leukemia are at increased risk of developing adverse body mass changes. Despite many studies, mechanisms of regulation of fat tissue metabolism are still poorly understood.

AREAS COVERED IN THIS REVIEW

The present article reviews the data from studies of leukemia survivors in the context of basic science studies and reports of nutritional situation in Europe published between 1994 and 2009. As regulation of appetite and energy balance is very complex, environmental, biochemical and genetic factors are presented.

WHAT THE READER WILL GAIN

Fat mass and obesity associated gene (FTO) has recently been found to contribute to the risk of obesity. The possible role of this gene as well as late consequences of body mass changes are discussed.

TAKE HOME MESSAGE

Both underweight and overweight leukemia survivors need to be monitored for ongoing health consequences of abnormal BMI. Parameters of metabolic syndrome should be included as routine assessments in outpatient clinics taking care of childhood leukemia survivors.

The FTO gene rs9939609 obesity-risk allele and loss of control over eating

BACKGROUND

Children with rs9939609 FTO variant alleles (homozygous = AA and heterozygous = AT) are predisposed to greater adiposity than are those with 2 wild-type alleles (TT).

OBJECTIVE

Because FTO is highly expressed in hypothalamic regions that are important for appetite, FTO genotype may affect energy balance by influencing eating behavior. Loss of control (LOC) eating, a behavior commonly reported by overweight youth, predicts excessive weight gain in children. However, the relation between FTO genotype and LOC eating has not been previously examined.

DESIGN

Two-hundred eighty-nine youth aged 6-19 y were genotyped for rs9939609, underwent body-composition measurements, and were interviewed to determine the presence or absence of LOC eating. A subset (n = 190) participated in a lunch buffet test meal designed to model an LOC eating episode. Subjects with AA and AT genotypes were grouped together for comparison with wild-type TT subjects.

RESULTS

Subjects with at least one A allele (67.7%) had significantly greater body mass indexes, body mass index z scores (P < 0.01), and fat mass (P < 0.05). Of the AA/AT subjects, 34.7% reported LOC compared with 18.2% of the TT subjects (P = 0.002). Although total energy intake at the test meal did not differ significantly by genotype (P = 0.61), AA/AT subjects consumed a greater percentage of energy from fat than did the TT subjects (P < 0.01).

CONCLUSIONS

Children and adolescents with 1 or 2 FTO rs9939609 obesity-risk alleles report more frequent LOC eating episodes and select foods higher in fat at a buffet meal. Both LOC eating and more frequent selection of energy-dense, palatable foods may be mechanisms through which variant FTO alleles lead to excess body weight.

Gene-environment interactions and obesity--further aspects of genomewide association studies

Advances in genotyping technologies have facilitated the advent of the genomewide association studies in large study populations and thereby led to the identification of an impressive-and still increasing-number of genetic variants with significant impact on the risk of widespread lifestyle health problems such as obesity, diabetes, and cardiovascular disease. Yet, the scientific community is a long way from reaching a comprehensive picture of the heritable components of these diseases and advancing from plain statistical significance into a biological understanding where the true contribution to a trait is recognized. Increasingly large study populations, denser single-nucleotide polymorphism mapping, deep sequencing, and raised awareness of the importance of structural variants may add to the known genetic variance underlying common complex disorders; however, genetic variance alone probably cannot account for disease susceptibility without the addition of pre- and postnatal environmental and/or behavioral factors. Moreover, an interaction between genetic and environmental factors may hinder the detection of genetic effects if not accounted for, e.g., in genomewide association studies, and prospective cohort studies have hence been proposed to surpass the classic case-control design. With a focus on obesity we describe some of the recently reported gene-environment interactions for polymorphisms identified in the FTO and INSIG2 genes. Ultimately, a thorough understanding of the gene-environment interactions underlying a common complex condition such as obesity may suggest novel treatment or intervention strategies to complement the harmful effect of detrimental genetic variation and thus may assist in improving the quality of life for affected individuals.

Measuring outcomes in a longitudinal birth cohort

Longitudinal studies are often focussed on specific outcomes to address predetermined hypotheses. Nevertheless, many discoveries have been made with data collected that were not part of the original design. Measurement of a broad range of outcomes is therefore important. Here we describe examples of the types of outcome that a birth cohort should collect, with emphasis on accuracy. We emphasise the use of continuous traits as well as of dichotomous outcomes, using a variety of examples.

Effects of the FTO gene on lifestyle intervention studies in children

The effects of FTO on body weight, body composition, and the risk of developing overweight and obesity in children, adolescents, and adults are analyzed in this review. Most trails have been conducted on the rs9939609 SNP of the FTO gene. The minor A-allele frequency ranged from 0.38 to 0.49 in different European populations. Briefly, it has been reported that overweight-obesity risk per A-allele ranged from 1.76 to 1.35, whereas z-score for BMI has a wider variation from 0.05 to 0.5 kg/m(2) in European children and adolescents. As for other adiposity indexes, a waist circumference increase from 0.60 to 0.95 cm per A-allele was found together with an increase in fat mass from 0.68 to 1.78 kg in European children and adoles-cents. In regard to food intake, AA carrier subjects were reported to have reduced satiety responsiveness scores and a higher total energy and fat intake. However, it is not clear whether energy expenditure did modify the role of the rs9939609 FTO gene variant in adiposity. Furthermore, few reports examined the influence of FTO gene variants using intervention studies. Overall, it seems that the A-allele (rs9939609 FTO) is associated with higher body weight gain. However, further studies into FTO gene variants in children and adults are needed.