REDUCED CARBOHYDRATE RATIO ENHANCES METABOLIC CHANGES ASSOCIATED WITH WEIGHT LOSS DIET Harn J. Shiue, Carl Sather, Don K. Layman; University of Illinois-Champaign-Urbana, 430 Bevier Hall, 905 S. Goodwin, Urbana, IL 61801 Weight loss associated with energy restriction is often associated with loss of muscle mass as well as body fat. This study evaluated effects of a diet with reduced CHO/Prot ratio on changes in body composition and protein metabolism. Twenty-four women, 45-56 years old and 10-30% above idea were selected to be consuming an average U.S. diet with ratios of CHO/Prot/Fat of 51/14/34. Women were paired based on age, weight, and hormone status and assigned to either a Protein Group (CHO/Prot ratio of 1.4) or a CHO Group (CHO/Prot 3.7). Diets were isocaloric (1660 kcal/d) and contained 50g fat/d. after 10 weeks, total weight loss for the Prot and CHO Groups were 7.53 kg and 6.96 kg, respectively. The Prot Group lost 18% more body fat and 27% less muscle mass (0.88 kg vs. 1/21 kg) compared to the CHO Group. The Prot Group maintained higher levels of thyroid hormone (T3 and T4) suggesting a higher BMR. Fasting plasma levels of branched-chain amino acids (BCAA) were 47% in the Prot Group. BCAA were further elevate after meals in the Prot Group. These changes were associated with a 21% increase in the post-prandial plasma alanine plus glutamine pool in the Prot Groups. Fasting blood urea levels were not different between groups. The meal response was proportional to protein intake with a 43% increase in the Prot Group and a 27% increase in the CHO Group. These findings suggest that weight loss on a moderate protein diet maintains thyroxine levels, increases plasma concentration of branched-chained amino acids, and enhances changes in body composition. (Sponsors: NCBA and Kraft) İFASEB* Journal 2001;15 (4 Part 1); A 301 *Federation of American Societies for Experimental Biology _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com