Inherited behavioral susceptibility to adiposity in infancy: a multivariate genetic analysis of appetite and weight in the Gemini birth cohort

Prevention of obesity in infancy and early childhood: a National Institutes of Health workshop

Addressing the childhood obesity epidemic continues to be a challenge. Given that once obesity develops it is likely to persist, there has been an increasing focus on prevention at earlier stages of the life course. Research to develop and implement effective prevention and intervention strategies in the first 2 years after birth has been limited. In fall 2013, the National Institute of Diabetes and Digestive and Kidney Diseases convened a multidisciplinary workshop to summarize the current state of knowledge regarding the prevention of infant and early childhood obesity and to identify research gaps and opportunities. The questions addressed included (1) "What is known regarding risk for excess weight gain in infancy and early childhood?" (2) "What is known regarding interventions that are promising or have been shown to be efficacious?" and (3) "What are the challenges and opportunities in implementing and evaluating behavioral interventions for parents and other caregivers and their young children?"

The Association of FTO SNP rs9939609 with Weight Gain at University

AIM

We tested the hypothesis that the obesity-associated FTO SNP rs9939609 would be associated with clinically significant weight gain (≥ 5% of initial body weight) in the first year of university; a time identified as high risk for weight gain.

METHODS

We collected anthropometric data from university students (n = 1,411, mean age: 22.4 ± 2.5 years, 49.1% male) at the beginning and end of the academic year. DNA was analysed for FTO rs9939609. Associations of FTO genotype with BMI at baseline were analysed using ANCOVA, and with risk of 5% weight gain over follow-up with logistic regression; both analyses adjusting for age and sex. The alpha level was reduced to 0.0125 to account for multiple testing.

RESULTS

Using an additive model, FTO status was not associated with higher BMI at baseline (22.2 vs. 21.9 kg/m2, p = 0.059). Dropout was high but unrelated to genotype. Among the 310 (21.9%) completing follow-up, those with AT genotypes had twice the odds of ≥ 5% weight gain compared with TTs (OR = 2.05, 95% CI = 1.05-4.01, p = 0.036), but this was no longer significant after Bonferroni correction. There was a trend for AA carriers for ≥ 5% weight gain compared with TT carriers (p = 0.089), but sample size was small.

CONCLUSION

This study provides nominal evidence for the genetic susceptibility hypothesis, but findings need to be replicated.

Differential maternal feeding practices, eating self-regulation, and adiposity in young twins

OBJECTIVE

Restrictive feeding is associated with childhood obesity; however, this could be due to other factors that drive children to overeat and parents to restrict (eg, child genetics). Using a twin design to better control for confounders, we tested differences in restrictive feeding within families in relation to differences in twins' self-regulatory eating and weight status.

METHODS

Sixty-four same-gender twin pairs (4-7 years old) were studied with their mothers. Child caloric compensation ability (COMPX% index) was assessed by using a laboratory-based protocol. The Child Feeding Questionnaire assessed mothers' self-reported feeding styles toward each twin. Child BMI (kg/m(2)) and BMI z score were calculated by using measured weight and height; percent body fat and waist circumference were also assessed. Partial correlations examined within-twin pair differences in Child Feeding Questionnaire subscales in relation to within-twin pair differences in anthropometry and caloric compensation (COMPX%).

RESULTS

Differences in maternal restriction were significantly associated with within-pair differences in child COMPX% and BMI z score. Mothers reported more restriction toward the heavier and more poorly compensating twin. Additionally, within-pair differences in parental pressure to eat were associated with significant differences in BMI z score, percent body fat, and waist circumference. Mothers were more pressuring toward the lighter twin.

CONCLUSIONS

Mothers vary in their feeding practices, even among same-gender twin pairs, which might influence differences in adiposity. Future research needs to elucidate cause-and-effect and intervention implications regarding parental restriction and pressure-to-eat prompts.

Association of eating speed and energy intake of main meals with overweight in Chinese pre-school children

OBJECTIVE

To investigate the association between eating behaviours (eating speed and energy intake of main meals) and overweight in pre-school children.

DESIGN

Cross-sectional study. Data consisted of measurements (height and weight), questionnaire information (eating behaviours of eating speed and overeating) and on-site observation data (meal duration and energy intake of main meals).

SETTING

Seven kindergartens in Beijing, China.

SUBJECTS

Pre-school children (n 1138; age range 3·1-6·7 years old) from seven kindergartens participated in the study.

RESULTS

The multivariate-adjusted odds ratio of overweight in participants with parent-reported 'more than needed food intake' was 3·02 (95 % CI 2·06, 4·44) compared with the 'medium food intake' participants, and higher eating speed was associated with childhood overweight. For the two observed eating behaviours, each 418·7 kJ (100 kcal) increase of lunch energy intake significantly increased the likelihood for overweight by a factor of 1·445, and each 5-min increase in meal duration significantly decreased the likelihood for overweight by a factor of 0·861. Increased portions of rice and cooked dishes were significantly associated with overweight status (OR = 2·274; 95 % CI 1·360, 3·804 and OR = 1·378; 95 % CI 1·010, 1·881, respectively).

CONCLUSIONS

Eating speed and excess energy intake of main meals are associated with overweight in pre-school children.

From modeling to measurement: developmental trends in genetic influence on adiposity in childhood

OBJECTIVE

Evidence of increasing heritability of BMI over childhood can seem paradoxical given longer exposure to environmental influences. Genomic data were used to provide direct evidence of developmental increases in genetic influence.

METHODS

BMI standard deviation scores (BMI-SDS) at ages 4 and 10 were calculated for 2,556 twin pairs in the Twins Early Development Study. Twin analyses estimated heritability of BMI-SDS at each age and the longitudinal genetic correlation. One randomly selected twin per pair was genotyped. Genome-wide complex trait analysis (GCTA) determined DNA-based heritability at each age and the longitudinal genomic correlation. Associations with a polygenic obesity risk score (PRS) using 28 obesity-related single nucleotide polymorphisms (SNPs) were assessed at each age, with bootstrapping to test the significance of the increase in variance explained.

RESULTS

Twin-estimated heritability increased from age 4 (0.43; 95% CI: 0.35-0.53) to 10 (0.82; 0.74-0.88). GCTA-estimated heritability went from non-significant at 4 (0.20; -0.21 to 0.61) to significant at 10 (0.29; 0.01-0.57). Longitudinal genetic correlations derived from twins (0.58) and GCTA (0.66) were similar. The same PRS explained more variance at 10 than 4 years (R(2) Δ:0.024; 0.002-0.078).

CONCLUSIONS

GCTA and PRS findings confirm twin-based results suggesting increasing genetic influence on adiposity during childhood despite substantial genetic stability.

Intergenerational impact of maternal obesity and postnatal feeding practices on pediatric obesity

The postnatal feeding practices of obese and overweight mothers may place their children at increased risk for the development of obesity through shared biology and family environments. This article reviews the feeding practices of obese mothers, describes the potential mechanisms linking maternal feeding behaviors to child obesity risk, and highlights the potential avenues of intervention. Strategies important for improving the quality of the eating environment and preventing the intergenerational transmission of obesity include supporting breastfeeding, improving the food choices of obese women, and encouraging the development of feeding styles that are responsive to hunger and satiety cues.

Moderate to vigorous physical activity interactions with genetic variants and body mass index in a large US ethnically diverse cohort

BACKGROUND

Little is known about the interaction between genetic and behavioural factors during lifecycle risk periods for obesity and how associations vary across race/ethnicity.

OBJECTIVE

The objective of this study was to examine joint associations of adiposity-related single-nucleotide polymorphisms (SNPs) and moderate to vigorous physical activity (MVPA) with body mass index (BMI) in a diverse adolescent cohort.

METHODS

Using data from the National Longitudinal Study of Adolescent Health (n = 8113: Wave II 1996; ages 12-21, Wave III; ages 18-27), we assessed interactions of 41 well-established SNPs and MVPA with BMI-for-age Z-scores in European Americans (EA; n = 5077), African-Americans (AA; n = 1736) and Hispanic Americans (HA; n = 1300).

RESULTS

Of 97 assessed, we found nominally significant SNP-MVPA interactions on BMI-for-age Z-score in EA at GNPDA2 and FTO and in HA at LZTR2/SEC16B. In EA, the estimated effect of the FTO risk allele on BMI-for-age Z-score was lower (β = -0.13; 95% confidence interval [CI]: 0.08, 0.18) in individuals with ≥5 vs. <5 (β = 0.24; CI: 0.16, 0.32) bouts of MVPA per week (P for interaction 0.02). Race/ethnicity-pooled meta-analysis showed nominally significant interactions for SNPs at TFAP2B, POC5 and LYPLAL1.

CONCLUSIONS

High MVPA may attenuate underlying genetic risk for obesity during adolescence, a high-risk period for adult obesity.

Satiety mechanisms in genetic risk of obesity

IMPORTANCE

A better understanding of the cause of obesity is a clinical priority. Obesity is highly heritable, and specific genes are being identified. Discovering the mechanisms through which obesity-related genes influence weight would help pinpoint novel targets for intervention. One potential mechanism is satiety responsiveness. Lack of satiety characterizes many monogenic obesity disorders, and lower satiety responsiveness is linked with weight gain in population samples.

OBJECTIVE

To test the hypothesis that satiety responsiveness is an intermediate behavioral phenotype associated with genetic predisposition to obesity in children.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional observational study of a population-based cohort of twins born January 1, 1994, to December 31, 1996 (Twins Early Development Study). Participants included 2258 unrelated children (53.3% female; mean [SD] age, 9.9 [0.8] years), one randomly selected from each twin pair.

EXPOSURE

Genetic predisposition to obesity. We created a polygenic risk score (PRS) comprising 28 common obesity-related single-nucleotide polymorphisms identified in a meta-analysis of obesity-related genome-wide association studies.

MAIN OUTCOMES AND MEASURES

Satiety responsiveness was indexed with a standard psychometric scale (Child Eating Behavior Questionnaire). Using 1990 United Kingdom reference data, body mass index SD scores and waist SD scores were calculated from parent-reported anthropometric data for each child. Information on satiety responsiveness, anthropometrics, and genotype was available for 2258 children. We examined associations among the PRS, adiposity, and satiety responsiveness.

RESULTS

The PRS was negatively related to satiety responsiveness (β coefficient, -0.060; 95% CI, -0.019 to -0.101) and positively related to adiposity (β coefficient, 0.177; 95% CI, 0.136-0.218 for body mass index SD scores and β coefficient, 0.167; 95% CI, 0.126-0.208 for waist SD scores). More children in the top 25% of the PRS were overweight than in the lowest 25% (18.5% vs 7.2%; odds ratio, 2.90; 95% CI, 1.98-4.25). Associations between the PRS and adiposity were significantly mediated by satiety responsiveness (P = .006 for body mass index SD scores and P = .005 for waist SD scores).

CONCLUSIONS AND RELEVANCE

These results support the hypothesis that low satiety responsiveness is one of the mechanisms through which genetic predisposition leads to weight gain in an environment rich with food. Strategies to enhance satiety responsiveness could help prevent weight gain in genetically at-risk children.

Responses to FTO genetic test feedback for obesity in a sample of overweight adults: a qualitative analysis

Current evidence indicates that genetic testing for obesity risk has limited affective or behavioral impact, but few studies have explored the effects among individuals who self-identify as having weight problems. Here, we report findings from in-depth telephone interviews with seven overweight or obese volunteers who were genotyped for one weight-related gene (FTO), which may offer interesting insights into motivations to seek out genetic testing and immediate reactions to it. All participants had a BMI > 25. The gene test identified one participant as homozygous for the 'higher-risk' variant (AA), three heterozygous (AT), and three homozygous for the 'lower-risk' variant (TT) of FTO. All participants said they took part to find an explanation for their personal struggle with weight control. Those with one or two higher-risk variants experienced relief and saw the result as confirming their private assumption that they were susceptible to weight gain for reasons perceived as 'external' to them. However, at the same time, they described themselves as more motivated to overcome their genetic predisposition. Those with lower-risk variants reported brief disappointment, but then focused on alternative explanations, reinforcing the multifactorial nature of obesity. Despite objectively low 'information value,' all individuals derived some 'personal' benefit from FTO genetic test feedback. However, improving education about the multifactorial nature of complex conditions is important to decrease polarized thinking and associated genetic determinism and stigma to derive the greatest benefits of novel genetic technologies for individuals and their health.

Dietary intake of young twins: nature or nurture?

BACKGROUND

The early years in life are increasingly recognized as a critical period for the development of diet-related behavioral traits. However, discussions continue on the relative role of genes and the environment in determining dietary intake, particularly in young children for whom detailed dietary information is limited.

OBJECTIVES

This study tested the hypothesis that diet in early childhood is primarily determined by the environment rather than by genes. A secondary aim was to characterize the early childhood diet.

DESIGN

A classic twin design used 3-d dietary data collected at age 21 mo from the Gemini cohort. From the full sample of 2402 families with twins, dietary diaries were available for 1216 twin pairs (384 monozygotic and 832 dizygotic pairs) after exclusions. Intakes of macronutrients, food, and beverages were estimated. Twin analyses quantified the contributions of genetic and environmental factors to population variation in intake.

RESULTS

At age 21 mo, children consumed small portions of a wide range of family foods. The shared environment was the predominant determinant, contributing between 66% (95% CI: 52%, 77%; milk-based desserts) and 97% (95% CI: 95%, 98%; juice) of the variation in intake. Genetic factors were estimated to account for between 4% (95% CI: 0%, 10%; savory snacks) and 18% (95% CI: 14%, 23%; bread) of dietary intake variation.

CONCLUSION

Shared environmental influences are the predominant drivers of dietary intake in very young children, indicating the importance of factors such as the home food environment and parental behaviors.

Genetic variation in the fat mass and obesity-associated gene (FTO) in association with food preferences in healthy adults

Background

Earlier studies have indicated that the fat mass and obesity-associated gene (FTO) is not only associated with BMI and weight but also with appetite and dietary intake.

Objectives

We investigated if the FTO rs9939609 associates with food preferences in healthy adults with no cancer, cardiovascular disease, or diabetes. Additionally, we challenged the question if the associations are modified by obesity status (BMI ≤25 or >25 kg/m²).

Design

The analyses are made with 22,799 individuals from the Swedish population-based Malmö Diet and Cancer Cohort Study, who were born between 1923 and 1945. To investigate food preference, 27 food groups conducted from a modified diet history method including a 7-day registration of cooked meals and cold beverages were used in the analyses. Bonferroni correction was used to correct for multiple testing, resulting in a cut-off value for significance level of p<0.002.

Results

We observed that the obesity susceptible A-allele carriers reported a higher consumption of biscuits and pastry but lower consumption of soft drinks (P for trend <0.0001 for both) as compared to TT genotype carriers. In contrast to our hypothesis, the results did not significantly differ depending on obesity status except for consumption of juice, where only the overweight individuals with A-allele had a higher consumption as compared to TT carriers (P for interaction=0.04).

Conclusion

Our results indicate that the FTO A-allele may associate with certain food preference and in particular with certain energy-dense foods.