Effect of an aerobic exercise training program on resting metabolic rate in chronically beta-adrenergic blocked...

There is substantial evidence that the use of beta-adrenergic receptor blockers (beta-blockers) is associated with a reduction in resting metabolic rate (RMR) and that a weight gain usually occurs in the first few months of treatment. The purpose of this study was to determine if RMR of overweight and sedentary subjects consuming beta-blockers can be increased following an aerobic exercise training program.

Twenty-four subjects participated in the study; 11 (6 women, 5 men) were treated with beta-blockers for hypertension and 13 (9 women, 4 men) were nonmedicated (control group). Body composition, RMR, and peak oxygen uptake (VO2peak) were assessed for all subjects before and after a 12-week aerobic exercise training program. Weekly exercise energy expenditure equaled 83.68 kJ (20 kcal) per kg of body weight while exercise intensity was maintained between 60% and 70% of the VO2 reserve.

Body composition, RMR, and VO2peak did not differ among groups at the beginning of the study. Body weight (-1.4 kg for beta-blockers, P < .05; -2.5 kg for control, P < .05) and VO2peak (+2.2 mL x kg(-1) x min(-1) for beta-blockers, P < .05; +4.1 mL x kg(-1) x min(-1) for control, P < .001) were significantly improved in both groups, whereas RMR (-272 kJ x day(-1) for beta-blockers, NS; +573 kJ x day(-1) for control, P < .05) was increased only in the control group after the aerobic exercise training program.

These results suggest that beta-blockers limit the increase in RMR normally observed following an aerobic exercise training program. Consequently, obtaining a negative energy balance in an attempt to lose weight may be more difficult.