HYPOCALORIC HIGH-PROTEIN DIET IMPROVES GLUCOSE-OXIDATION AND SPARES LEAN BODY-MASS - COMPARISON TO HYPOCALORIC HIGH-CARBOHYDRATE DIET

The aim of the study was to investigate the effects of two hypocaloric (800-kcal) diets on body weight reduction and composition, insulin se nsitivity, and proteolysis in 25 normal glucose-tolerant obese women. The two diets had the following composition: 45% protein, 35% carbohyd rate (CHO), and 20% fat (HP diet, 10 subjects), and 60% CHO, 20% prote in, and 20% fat (HC diet, 15 subjects); both lasted 21 days. A euglyce mic hyperinsulinemic (25 mU/kg/h) clamp lasting 150 minutes combined w ith indirect calorimetry was performed before and after the diet. Both diets induced a similar decrease in body weight and fat mass (FM), wh ereas fat-free mass (FFM) decreased only after the HC diet. 3-Methylhi stidine (3-CH3-HIS) excretion was reduced by 48% after the HP diet and remained unchanged after the HC diet (P < .05). A significant correla tion was found between the changes in FFM and in 3-CH3-HIS excretion a fter the diet (r(s) = .50, P < .02). Blood glucose remained unchanged, while insulin decreased in both diets. Free fatty acids (FFA) signifi cantly increased only after the HC diet (P < .05). During the clamp pe riod, glucose disposal and glucose oxidation significantly increased a fter the HP diet and significantly decreased after the HC diet. Opposi te results were found when measuring lipid oxidation. In conclusion, o ur experience suggests that (1) a hypocaloric diet providing a high pe rcentage of natural protein can improve insulin sensitivity; and (2) c onversely. a hypocaloric high-polysaccharide-CHO diet decreases insuli n sensitivity and is unable to spare muscle tissue.