Aerobic exercise (AEX) intensity may be an important factor affecting the selective loss of abdominal fat when combined with a hypocaloric diet (DIET). The goal of this study is to determine the cellular mechanisms by which AEX intensity affects the loss of abdominal (both subcutaneous and visceral) adipose tissue under conditions of equal energy deficit in postmenopausal women with abdominal obesity. The hypothesis is that, compared to DIET alone or DIET with low-intensity AEX, DIET with high-intensity AEX will augment the loss of abdominal fat and improvements in metabolic cardiovascular disease (CVD) risk factors due to greater reductions in lipoprotein lipase (LPL) activity, and to greater increases in lipolysis, in abdominal, relative to gluteal, adipose tissue.
The specific aims are: 1) to determine the cellular mechanisms by which DIET alone, or DIET combined with low- or high-intensity AEX, affects region-specific fat loss by measuring changes in abdominal and gluteal adipose tissue LPL activity and lipolysis in postmenopausal women with abdominal obesity; and 2) to determine the effects of DIET alone, or DIET combined with low- or high-intensity AEX on lipoprotein lipids, glucose tolerance, and insulin levels in these women. We also will measure messenger ribonucleic acid (mRNA) levels of genes that may be involved in the regulation of regional fat storage to begin to determine how DIET with and without AEX of different intensities affects gene expression to alter body fat distribution. Body composition and fat distribution (DXA and computed tomography), LPL activity, lipolysis, mRNA expression of genes from gluteal and abdominal adipose tissue, and lipoprotein lipids and glucose tolerance will be measured before and after six months of DIET with high-intensity AEX, DIET with low-intensity AEX, or DIET alone in 120 (40 per treatment group) overweight (BMI=25-35 kg/m2), postmenopausal women with abdominal obesity (waist circumference greater than 88 cm). The degree of caloric restriction during DIET will be adjusted so that total caloric deficit (about 2800 kcals/wk) will be similar between treatments. Both AEX groups will expend 400 kcal/wk in exercise energy expenditure and will reduce dietary intake by about 2400 kcal/wk (about 340 kcal/day). Identification of the mechanisms by which DIET with and without AEX of different intensities affects regional uptake and mobilization of triglyceride to alter body fat distribution will have important clinical implications for the development of the most effective treatment to promote the preferential loss of abdominal fat and improve CVD metabolic risk factors in older women with abdominal obesity.
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