Ability to Adjust Nocturnal Fat Oxidation in Response to Overfeeding Predicts 5-year Weight Gain in Adults

OBJECTIVE: To determine whether metabolic responses to short-term overfeeding predict longitudinal changes in body weight. METHODS: 24h energy expenditure (EE) and substrate utilization were measured at baseline in a room calorimeter following 3d of eucaloric and hypercaloric feeding (40% excess) in a sample of lean adults (n: 34; age: 28±2 years; body mass index: 22±3 kg/m(2)). Body mass and fat mass (DXA) were measured annually for 5yrs. Regression analyses examined whether changes in EE and fuel use with overfeeding predicted body weight and composition changes over 5yrs. RESULTS: Overfeeding increased EE and reduced fat oxidation when examined over the 24h, waking, and nocturnal periods. Absolute change in body mass over 5y was 3.0±0.6 kg (average rate of change = 0.7±0.1 kg per year, p<0.001). Lower nocturnal (but not 24h or waking) fat oxidation (r =−0.42, p=0.01) and EE (r=−0.33, p =0.05) with overfeeding were the strongest predictors of 5y weight gain. When adjusted for covariates, changes in nocturnal fat oxidation and EE with overfeeding predicted 41% of the variance weight change (p=0.02). CONCLUSIONS: Failure to maintain fat oxidation at night following a period of overfeeding appears to be associated with a metabolic phenotype favoring weight gain.