BACKGROUND: Accumulating evidence suggests that both dietary restriction and exercise (DR+E) should be incorporated in weight loss interventions to treat obese, older adults. However, more information is needed on the effects to lower extremity tissue composition-an important consideration for preserving mobility in older adults. METHODS: Twenty-seven sedentary women (body mass index 36.3 +/- 5.4kg/m2; age 63.6 +/- 5.6 yrs) were randomly assigned to 6 months of DR+E or a health education control group. Thigh and calf muscle, subcutaneous adipose tissue (SAT), and intermuscular adipose tissue (IMAT) size were determined using magnetic resonance imaging. Physical function was measured using a long-distance corridor walk and knee extension strength. RESULTS: Compared with control, DR+E significantly reduced body mass (-6.6 +/- 3.7kg versus control -0.05 +/- 3.5kg; p < 0.01). Thigh and calf muscle volumes responded similarly between groups. Within the DR+E group, adipose tissue was reduced more in the thigh than in the calf (p < 0.04). Knee extension strength was unaltered by DR+E, but a trend toward increased walking speed was observed in the DR+E group (p = 0.09). Post hoc analyses showed that reductions in SAT and IMAT within the calf, but not the thigh, were associated with faster walking speed achieved with DR+E (SAT r = -0.62; p = 0.01; IMAT r = -0.62; p = 0.01). CONCLUSIONS: DR+E preserved lower extremity muscle size and function and reduced regional lower extremity adipose tissue. Although the magnitude of reduction in adipose tissue was greater in the thigh than the calf region, post hoc analyses demonstrated that reductions in calf SAT and IMAT were associated with positive adaptations in physical function.
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