Common etiological architecture underlying reward responsiveness, externally driven eating behaviors and BMI in childhood: findings from the Gemini twin cohort

BACKGROUND: Studies have reported that impulsivity predicts childhood BMI and that the association is mediated by eating behaviors. One aspect of impulsivity – potentially crucial in the obesity context – is reward responsiveness, which may predispose to responsiveness to palatable food cues. The behavioral susceptibility theory hypothesizes that genetic susceptibility to obesity operates partly via genetically determined differences in appetite regulation. Reward responsiveness may therefore be one of the neuro-endophenotypes that mediates genetic susceptibility to obesity. OBJECTIVE: To test whether reward responsiveness, eating behaviors and child BMI share common genetic architecture. METHODS: We examined reward responsiveness, eating behaviors and BMI in five-year-old children from Gemini, a UK birth cohort of 2,402 twin pairs born in 2007. All measures were collected by parent report. Reward responsiveness was derived from the Behavioral Approach System. Compulsion to eat and eating for pleasure was measured with the ‘food responsiveness’ scale of the Child Eating Behavior Questionnaire. Wanting to eat in response to environmental food cues was measured with the ‘external eating’ scale of the Dutch Eating Behavior Questionnaire. Maximum-likelihood structural equation modelling was used to establish underlying common genetic and environmental influences. RESULTS: There were significant positive phenotypic correlations between all traits except for reward responsiveness and BMI. Genetic factors explained the majority of the association between food responsiveness and external eating (74%, 95%CI: 61, 87), whereas common shared environmental factors explained the majority of the associations between reward responsiveness with both food responsiveness (55%, 95%CI: 20, 90) and external eating (70%, 95%CI: 39, 100). CONCLUSIONS: Our study demonstrates the importance of common environmental factors in the shared etiology between reward responsiveness and childhood eating behaviors. However, the common etiology underlying both reward responsiveness and BMI is unclear, as there was no phenotypic correlation between reward responsiveness and BMI at this age. Further longitudinal research needs to detangle this complex relationship throughout development.