AUTONOMIC NERVOUS-SYSTEM ACTIVITY IN WEIGHT-GAIN AND WEIGHT-LOSS

Studies in both animals and humans indicate that the autonomic nervous system (ANS) responds to changes in systemic energy balance. In the p resent study, ANS response to weight change was examined by sequential blockade of cardiac autonomic innervation with parasympathetic (atrop ine) and sympathetic (esmolol) blockers. Change in heart period (inter beat interval) from baseline after atropine defined the amount of para sympathetic control (PC), and the subsequent change after esmolol defi ned the amount of sympathetic control (SC). In nonobese subjects, weig ht gain to 10% above initial body weight resulted in a decrease in PC and an increase in SC, and conversely, weight loss to 10% below initia l weight resulted in an increase in PC and a decrease in SC. In obese subjects, weight loss resulted in the same pattern of changes in PC an d SC. The major changes were in the parasympathetic arm of the ANS. Th ese findings support the hypothesis that the ANS acts to oppose weight change.