Effect of overeating on plasma and urinary concentrations of norepinephrine

This study examined the effect of overeating on plasma norepinephrine concentrations and urinary norepinephrine excretion in man, since overeating sucrose or fat increases norepinephrine turnover in rodents. Five normal subjects were overfed by 50% for 20 days, without substantially changing the proportions of protein, fat, and carbohydrate in the diet, after a control period of normal feeding. Sodium intake remained constant throughout the study. There was no effect of overfeeding on plasma norepinephrine concentrations when subjects were resting supine either before or after a meal. However, plasma norepinephrine concentrations after 10 min of orthostasis were 40% lower (P less than 0.05) at the end of overfeeding. Plasma norepinephrine concentrations during slow walking also tended to be lower during overfeeding, but this effect was not statistically significant. Mean 24-h norepinephrine and epinephrine excretion were not altered. These data do not support the hypothesis that overeating increases sympathetic nervous system activity in man.