Heredity and overfeeding-induced changes in submaximal exercise VO2

The present study investigated the role of heredity in determining changes in the energy cost of submaximal exercise in response to short-term overfeeding. Six pairs of monozygotic twins were subjected to a 1,000 kcal/day surplus for 22 days with careful experimental controls over food intake and physical activities. O2 consumption (VO2) was measured during a submaximal treadmill exercise test 165 min postprandially before and the morning after the overfeeding protocol. As expected, overfeeding induced significant increases in body weight and fat mass. No significant increase in mean exercise VO2 was observed after overfeeding. However, the interindividual variation in overfeeding-induced changes in exercise VO2 was large and not randomly distributed. When comparing intrapair variance for changes in exercise VO2 to interpair variance, a moderate to high within-pair resemblance in response, i.e., a genotype-overfeeding interaction, was observed. Changes in exercise VO2 were positively correlated with those in postexercise levels of blood catecholamines, particularly epinephrine. A negative correlation was found between changes in exercise VO2 and body fat gain. These results are consistent with the concept of a role for the sympathoadrenal system in the regulation of adaptive thermogenesis and the predisposition to store fat. Moreover, these data suggest that the sensitivity to adapt in exercise energy expenditure after overfeeding is inherited to a significant extent.