Resting sympathetic activity is associated with the sympathetically mediated component of energy expenditure following a meal

Individuals with high plasma norepinephrine ( NE ) levels at rest have a smaller reduction in resting energy expenditure ( REE ) following β ‐adrenergic blockade. If this finding extends to the response to a meal, it could have important implications for the role of the sympathetic nervous system in energy balance and weight gain. We hypothesized high muscle sympathetic nerve activity ( MSNA ) would be associated with a low sympathetically mediated component of energy expenditure following a meal. Fourteen young, healthy adults completed two visits randomized to continuous saline (control) or intravenous propranolol to achieve systemic β ‐adrenergic blockade. Muscle sympathetic nerve activity and REE were measured (indirect calorimetry) followed by a liquid mixed meal (Ensure). Measures of energy expenditure continued every 30 min for 5 h after the meal and are reported as an area under the curve ( AUC ). Sympathetic support of energy expenditure was calculated as the difference between the AUC during saline and β ‐blockade ( AUC P ropranolol – AUC S aline , β ‐ REE ) and as a percent (%) of control ( AUC P ropranolol ÷ AUC S aline  × 100). β ‐ REE was associated with baseline sympathetic activity, such that individuals with high resting MSNA (bursts/100 heart beats) and plasma NE had the greatest sympathetically mediated component of energy expenditure following a meal ( MSNA : β ‐ REE R  =   −0.58, P =  0.03; % REE R  = −0.56, P =  0.04; NE : β ‐ REE R  = −0.55, P  = 0.0535; % REE R  = −0.54, P  = 0.0552). Contrary to our hypothesis, high resting sympathetic activity is associated with a greater sympathetically mediated component of energy expenditure following a liquid meal. These findings may have implications for weight maintenance in individuals with varying resting sympathetic activity.