Polymorphisms in the Fat Mass and Obesity Associated (FTO) gene are robustly associated with overweight and obesity among children, although the underlying mechanisms are poorly understood. We tested if appetitive traits partially mediated the association between FTO genotype and increased BMI among a sample of US preadolescents. Data were from 178 unrelated 9-10 year olds who participated in an experimental study between 2013 and 2015. Children's DNA was isolated from buccal swabs, and the rs9939609 SNP in the FTO gene was genotyped. Children's age- and sex-adjusted BMI z-scores were computed using height and weight measured at the laboratory. Parents completed the Child Eating Behavior Questionnaire that includes three validated scales of habitual appetitive traits related to drive and regulation: satiety responsiveness, enjoyment of food and food responsiveness. Structural equation modeling was used to assess if those traits mediated the relationship between FTO and BMI z-score. The sample of children was 48.9% male and 91.0% non-Hispanic white. FTO distribution was in Hardy Weinberg equilibrium, and 16.3% of participants were homozygous for the high-risk allele. Mean BMI z-score was greatest among those with the high-risk genotype (ANOVA P < 0.01). In separate structural equation models adjusted for the child's sex and maternal education, decreased satiety responsiveness and increased food responsiveness each partially mediated the positive association between the high-risk genotype and increased BMI z-score (P-value for each indirect effect <0.05). Continued research is needed to better understand how other known genetic obesity risk factors may impact appetitive traits among children.
