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.