URBANA, Ill.--According to a study published in the August issue of the Journal of Nutrition (8, 135:1903-1910), a weight-loss diet with a higher protein-to-carbohydrate ratio may facilitate greater fat loss and preserve more lean muscle mass than a weight-loss diet with a higher carbohydrate to protein ratio.
Researchers examined the interaction of two diets--a high protein, low carbohydrate diet (PRO) vs. a low protein, high carbohydrate diet (CHO)--plus exercise on body composition and blood lipids in women (n = 48, 46 y old, BMI = 33 kg/m2) during weight loss. Diets were equal in total energy (7.1 mJ/d) and lipids (30 percent energy intake) but differed in protein content and the ratio of carbohydrates to protein at 1.6 g/d and <1.5 (PRO group) vs. 0.8 g/d and >3.5 (CHO group), respectively. PRO and CHO subjects also either adhered to an active lifestyle (control) or a supervised exercise program (EX: five d/wk walking and two d/wk resistance training).
At the end of four months, subjects in the PRO and PRO + EX groups lost more total weight and fat mass and tended to lose less lean mass than the CHO and CHO + EX groups. Exercise increased loss of body fat and preserved lean mass. The combined effects of diet and exercise were additive for improving body composition. Serum lipid profiles improved in all groups, but changes varied among diet treatments. Subjects in the CHO groups had larger reductions in total cholesterol and LDL cholesterol, whereas subjects in the PRO groups had greater reductions in triacylglycerol and maintained higher concentrations of HDL cholesterol.
Researchers concluded a diet with higher protein and reduced carbohydrates combined with exercise additively improved body composition during weight loss, whereas the effects on blood lipids differed between diet treatments.