Effects of energy restriction and exercise on skeletal muscle and adipose tissue in women as measured by magnetic resonance imaging.

The effects of energy restriction alone (diet alone, DO) and energy restriction combined with endurance exercise (diet and exercise, DE) on lean tissue (LT), skeletal muscle (SM), and adipose tissue (AT) were evaluated in 24 obese women (DO, n = 12; DE, n = 12). The prescribed diet created an estimated daily deficit of 4.19 MJ (1000 kcal). LT, SM, and AT were measured by using magnetic resonance imaging (MRI). The weight loss observed for the DO group (-10.0 +/- 4.0 kg) was not significantly different from that of the DE group (-11.7 +/- 3.0 kg). However, the composition of the weight loss was significantly different between groups because the DE group lost significantly greater (P = 0.05) quantities of AT (-11.3 +/- 3.8 L) than the DO group (-8.3 +/- 3.6 L). Furthermore, whereas LT measured by MRI was maintained in the DE group, a modest (approximately 4%) but significant (P < 0.01) reduction in LT was observed in the DO group. Similarly, measurement of SM by MRI in the appendicular region revealed a preservation of SM in the DE group, but a significant (P < 0.01) reduction in the DO group. Maximal oxygen consumption (L) was significantly improved (approximately 9%) in the DE group (P < 0.01). These findings provide evidence that the combination of energy restriction and exercise result in a greater reduction of AT and preservation of LT and SM compared with energy restriction alone.