EXERCISE TRAINING ELEVATES RMR DURING MODERATE BUT NOT SEVERE DIETARY RESTRICTION IN OBESE MALE-RATS

This study examined the effects of 11 wk of exercise training (E) on resting O2 uptake (RMR) and the composition of diet-induced weight loss in obese male Sprague-Dawley rats (n = 48). The rats underwent one of three levels of dietary treatment: ad libitum (AL), moderate restriction (MR), and severe restriction (SR). Compared with AL-CC (cage confined; 647 +/- 13 g), the AL-E (84% of AL-CC), MR-CC (77%), MR-E (77%), SR-CC (63%), and SR-E (63%) groups were all reduced in body mass. At the MR level, E significantly reduced fat mass (FM; MR-CC 73 +/- 5, MR-E 45 +/- 5 g) and increased water mass (WM; MR-CC 307 +/- 5, MR-E 329 +/- 5 g) compared with CC. In contrast, no significant differences existed between the SR-CC and SR-E groups. Exercise training did not result in conservation of protein mass at any level of dietary intake. Exercise training significantly elevated RMR (on a kg0.75 basis) by approximately 7% for the AL-E and MR-E groups compared with their respective dietary counterparts. These findings may help reconcile the conflicting results present in the literature with respect to the effects of exercise training during diet-induced weight loss. That is, studies using relatively severe dietary restrictions are less likely to demonstrate exercise-induced changes in RMR, FM, and WM than those employing moderate dietary restrictions.