718 Am IC/in Nutr l986;44:7l8-24. Printed in USA. © 1986 American Society for Clinical Nutrition Original Research Communications-general Some metabolic effects of overeating in man13

ABSTRACT Metabolic responses to 20 days of overeating were examined in five healthy vol-unteers. Overfeeding caused a variable increase (1-18%) in basal metabolic rate but no change in metabolic rate during light exercise. Postprandial resting metabolic rate was 8-40 % higher (mean 18%) during overeating. The increase in oxygen consumption during a norepinephrine infusion was the same before (20 ± 2%) and after (17 ± 3%) overfeeding. Overfeeding elevated basal insulin concentrations in all subjects and increased the insulin response to intravenous glucose in four of five subjects. Overfeeding did not significantly alter mean serum T3 concentrations or erythrocyte Rb uptake (an index of Na,K-ATPase activity). These data do not confirm reports that overfeeding increases metabolic rate more during exercise than during rest. They also suggest that the increase in resting metabolic rate during overfeeding is not caused by increased responsiveness to norepinephrine or increased serum T3 concentrations. Am I Clin Nutr 1986; 44:718-24. KEY WORDS Overeating, metabolic rate, norepinephrine, T3, ATPase activit