Associations Among Dietary Fat Oxidation Responses to Overfeeding and Weight Gain in Obesity-Prone and Resistant Adults.

Abstract

OBJECTIVE:We tested the hypothesis that three days of overfeeding (OF) decreases dietary fat oxidation and predicts longitudinal weight change in adults classified as obesity-prone (OP) and obesity-resistant (OR) based on self-identification, personal and family weight history. Changes in diurnal profiles of plasma metabolites and hormones were measured to probe mechanisms.METHODS:Adults identified as OP (n=22; BMI: 23.9 ± 2.4 kg/m2) and OR (n=30; BMI: 20.5 ± 2.2 kg/m2) completed 3 days of eucaloric (EU) feeding and 3 days of OF. On day three, 24-hr total and dietary fat oxidation were measured using room calorimetry and an oral 14C tracer. Plasma glucose, insulin, triglycerides (TG), and non-esterified fatty acid (NEFA) concentrations were frequently sampled over 24-hr. Body composition was measured annually for 4.0 ± 1.4 years in a sub-sample (n=19 OP and 23 OR).RESULTS:Dietary fat oxidation over 24-hr was not altered by OF versus EU (P=0.54). Weight gain in OP correlated with lower nocturnal NEFA concentrations during OF (r=−0.60, P=0.006) and impaired fuel selection over 24-hr (metabolic inflexibility, wake RQ-sleep RQ) (r=−0.48, P=0.04).CONCLUSIONS:Short-term OF did not alter dietary fat oxidation. Lower nocturnal NEFA availability and metabolic inflexibility to overfeeding may be factors contributing to weight gain.