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: Twenty-four-hour energy expenditure (EE) and substrate utilization were measured at baseline in a room calorimeter following 3 days of eucaloric and hypercaloric feeding (40% excess) in a sample of lean adults (n: 34; age: 28 ± 2 y; BMI: 22 ± 3 kg/m ). Body mass and fat mass (dual-energy x-ray absorptiometry) were measured annually for 5 years. Regression analyses examined whether changes in EE and fuel use with overfeeding predicted body weight and composition changes over 5 years.

Results: Overfeeding increased EE and reduced fat oxidation when examined over the 24-hour, waking, and nocturnal periods. Absolute change in body mass over 5 years was 3.0 ± 0.6 kg (average rate of change = 0.7 ± 0.1 kg/y, P < 0.001). Lower nocturnal (but not 24-hour 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 5-year weight gain. When adjusted for covariates, changes in nocturnal fat oxidation and EE with overfeeding predicted 41% of the variance in 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.