Intermuscular adipose tissue (IMAT) and visceral adipose tissue (VAT) are associated with insulin resistance. We sought to determine whether exercise-induced weight loss (EX) results in greater reductions in IMAT and VAT compared with similar weight loss induced by calorie restriction (CR) and whether these changes are associated with improvements in glucoregulation. Sedentary men and women (50 to 60 yr; body mass index of 23.5 to 29.9 kg/m2) were randomized to 1 yr of CR (n = 17), EX (n = 16), or a control group (CON; n = 6). Bilateral thigh IMAT and VAT volumes were quantified using multi-slice magnetic resonance imaging. Insulin sensitivity index (ISI) was determined from oral glucose tolerance test glucose and insulin levels. Weight loss was comparable (p = 0.25) in the CR (-10.8 +/- 1.4%) and EX groups (-8.3 +/- 1.5%) and greater than in the control group (-2.0 +/- 2.4%; p < 0.05). IMAT and VAT reductions were larger in the CR and EX groups than in the CON group (p <= 0.05). After controlling for differences in total fat mass change between the CR and EX groups, IMAT and VAT reductions were nearly twofold greater (p <= 0.05) in the EX group than in the CR group (IMAT -45 +/- 5 versus -25 +/- 5 ml; VAT -490 +/- 64 versus -267 +/- 61 ml). In the EX group, the reductions in IMAT were correlated with increases in ISI (r = -0.71; p = 0.003), whereas in the CR group, VAT reductions were correlated with increases in ISI (r = -0.64; p = 0.006). In conclusion, calorie restriction and exercise-induced weight loss both decrease IMAT and VAT volumes. However, exercise appears to result in preferential reductions in these fat depots.

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