Effect of Exercise Amount and Intensity on Change in Adipose Tissue and Skeletal Muscle Distribution

Abstract

PURPOSE: Habitual exercise is associated with marked reduction in both total and abdominal adipose tissue (AT); however, the optimal dose (amount and intensity) of exercise required to elicit the greatest reduction remains unclear. The purpose of this investigation is to determine the separate effects of increasing exercise amount and intensity on AT and skeletal muscle (SM) mass in sedentary, abdominally obese adults. METHODS: Participants in this ancillary study included 105 men (40%) and women (60%) who were randomly assigned to one of four conditions for 24 weeks: control (C; n=20); low amount low intensity (LALI; 180 and 300 kcal/session for women and men, respectively, at 50% of VO2peak, n=24); high amount low intensity (HALI; 360 and 600 kcal/session for women and men respectively at 50% VO2peak, n=31); high amount high intensity (HAHI; 360 and 600 kcal/session for women and men, respectively, at 75% of VO2peak, n=30). AT and SM mass were measured by magnetic resonance imaging at baseline and 24 weeks. RESULTS: Reductions in total AT (%; C, -0.2; LALI, -7.9; HALI, -10.8; HAHI, -11.5), abdominal subcutaneous AT (%; C, -0.3; LALI, -6.7; HALI, -10.1; HAHI, -12.9), visceral AT (%; C, -0.2; LALI, -15.5; HALI, -18.4; HAHI, -17.1), weight (%; C, -0.8; LALI, -4.7; HALI, -6.8; HAHI, -6.4) and waist circumference (%; C, -1.2; LALI, -4.5; HALI, -6.1; HAHI, -5.6) were greater in all exercise groups compared to control (p<0.0001), independent of age and sex. Reductions in total AT and abdominal subcutaneous AT were greater in HAHI compared to LALI (p=0.003). SM mass did not change at 24 weeks in any exercise group compared to control (p>0.05). CONCLUSION: Substantial reduction in visceral AT with a preservation of SM mass is observed independent of exercise amount and intensity; however, higher intensity (HAHI) may be more effective than guideline-recommended (LALI) exercise for reducing total and subcutaneous adiposity. Supported by Canadian Institutes of Health Research (grant OHN-63277)