Coronary heart disease (CHD) mortality is strikingly high for black women, and is linked to several CHD risk factors, including excess body fat. Fat deposited 'centrally' as visceral adipose tissue (VAT) is a predisposing condition for metabolic CHD risk factors including insulin resistance, dyslipidemia, and hypertension. Fat visible within the muscle fascia as intermuscular adipose tissue (IMAT) is a newly studied fat depot associated with insulin resistance. Neither VAT or IMAT have been well-studied relative to CHD risk in black women. Using whole-body magnetic resonance imaging (MRI), pilot data comparing VAT and IMAT depots in 170 black and white women revealed that for the women at higher levels of body fatness, black women had significantly lower VAT and significantly higher IMAT than white counterparts (adjusted for total body fat). The broad long-term objective of this study is to determine whether reductions in VAT and IMAT relate to changes in the metabolic CHD risk profiles (fasting glucose and insulin, plasma lipid, lipoprotein, apolipoprotein, C-reactive protein, resting blood pressure) in weight-reduced premenopausal black women. Weight loss will be attained through a low saturated fat, energy-restricted diet and supervised endurance and resistance exercise. Seventy-five overweight/obese premenopausal black women will be randomly assigned to 1) energy-restricted diet, 2) combined energy-restricted diet and exercise, or 3) no treatment control for 14 weeks.
The specific aim of this study is to establish whether improvements in CHD risk factors in overweight/obese premenopausal black women are more closely related to weight loss-induced changes in IMAT than VAT or total adipose depots. A secondary aim is to compare the effects of diet vs. diet and exercise on changes in IMAT and VAT, after adjusting for changes in total adipose tissue. Study participants will be recruited from York College and the neighboring Queens, New York community. Body fat will be assessed by MRI, and metabolic CHD risk factors by physical examination and blood chemistry. Establishing the clinical importance of IMAT as a fat depot linked to CHD risk factors in premenopausal black women could lead to strategies to decrease CHD risk.
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