The decline in resting metabolic rate (RMR) during periods of caloric restriction is a well documented phenomenon. The purpose of this study was to determine if either 30 min of daily self-selected aerobic activity (group D) or prescribed exercise training performed every other day (group P) for 12 weeks can prevent the decrease in RMR during caloric restriction for weight loss. Seventy-eight adult subjects (38 M, 40 F) whose weights were 15 to 35 percent above the upper limit for age, sex and frame were randomly assigned to three treatment groups. All three groups followed the same 1,200, 1,500 or 1,800 kcal/d (5,023, 6,279, 7,534 kJ) diet exchange plan. Group C (control) followed no exercise program, while D and P exercised as described above. Maximal oxygen consumption (VO2max, mL/kg/min) predicted from the Bruce Test increased by 0.08 +/- 7, 9 +/- 12 and 12 +/- 9 percent in groups C, D and P, respectively. The increases for D and P were significantly higher than for C (p < 0.01). RMR (mL/kg/min) increased by 2 +/- 9, 4 +/- 7 and 10 +/- 9 percent in groups C, D and P respectively. The percent change for group P was significantly greater than that for groups C and D (p < 0.05). There was a significant relationship across all subjects between the % change in VO2max and % change in RMR (r = 0.307, p < 0.01). However, the association between these two variables was stronger for females than for males. Therefore, the incorporation of any level of exercise, even moderate daily activity may be of greater importance for females to prevent the decline in RMR during caloric restriction for weight loss.

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