Effects of short-term carbohydrate or fat overfeeding on energy expenditure and plasma leptin concentrations in healthy female subjects

OBJECTIVE: To determine the effects of excess carbohydrate or fat intake on plasma leptin concentrations and energy expenditure, DESIGN: Ten healthy lean females were studied: (a) during a 3 day isoenerge tic diet (ISO); (b) during 3 day carbohydrate overfeeding (CHO OF); and (c) during 3 day fat overfeeding (FAT OF). During each test, basal metabolic r ate, the energy expended during mild physical activity and recovery, and 24 h energy expenditure (24 h EE) were measured with indirect calorimetry. Th e concentrations of glucose and lactate were monitored in subcutaneous inte rstitial fluid over a 24 h period using microdialysis. Plasma hormone and s ubstrate concentrations were measured in a brood sample collected in the mo rning of the fourth day. RESULTS: CHO OF increased plasma leptin concentrations by 28%, and 24 h EE by 7%. Basal metabolic rate and the energy expended during physical activit y were not affected. FAT OF did not significantly change plasma leptin conc entrations or energy expenditure. There was no relationship between changes in leptin concentrations and changes in energy expenditure, suggesting tha t leptin is not involved in the stimulation of energy metabolism during ove rfeeding. Interstitial subcutaneous glucose and lactate concentrations were not altered by CHO OF and FAT OF. CONCLUSIONS: CHO OF, but not FAT OF, increases energy expenditure and lepti n concentration.