Metabolic Consequences of Very-Low-Calorie Diet Therapy in Obese Non-insulin-dependent Diabetic and Nondiabetic Subjects

Abstract

To determine the effects of very-low-calorie diets on the metabolic abnormalities of diabetes and obesity, we have studied 10 obese, non-insulin-dependent diabetic (NIDDM) and 5 obese, nondiabetic subjects for 36 days on a metabolic ward during consumption of a liquid diet of 300 kcal/day with 30 g of protein. Rapid improvement occurred in the glycemie indices of the diabetic subjects, with mean (± SEM) fasting plasma glucose falling from 291 ± 21 to 95 ± 6 mg/dl (P < 0.001) and total glycosylated hemoglobin from 13.1 ± 0.7% to 8.8 ± 0.3% (P < 0.001) (normal reference range 5.5–8.5%). Lipid elevations were normalized with plasma triglycerides reduced to <100 mg/dl and total plasma cholesterol to < 150 mg/dl in both groups. Hormonal and substrate responses were also comparable between groups with reductions in insulin and triiodothy-ronine and moderate elevations in blood and urinary ketoacid levels without a corresponding rise in free fatty acids. Electrolyte balance for sodium, potassium, calcium, and phosphorus was initially negative but approached equilibrium by completion of the study. Magnesium, in contrast, remained in positive balance in both groups throughout. Total nitrogen loss varied widely among all subjects, ranging from 70 to 367 g, and showed a strong positive correlation with initial lean body mass (N = 0.83, P < 0.001) and total weight loss (N = 0.87, P < 0.001). The nondiabetic group, which had a significantly greater initial body weight and lean body mass than the diabetic group, also had a significantly greater weight loss of 450 ± 31 g/day compared with 308 ± 19 g/day (P < 0.01) in the diabetic subjects. The composition of the weight lost at completion was similar in both groups and ranged from 21.6% to 31.3% water, 3.9% to 7.8% protein, and 60.9% to 74.5% fat. The contribution of both water and protein progressively decreased and fat increased, resulting in unchanged caloric requirements during the diet. This study demonstrates that short-term treatment with a very-low-calorie diet in both obese diabetic and nondiabetic subjects results in: (1) safe and effective weight loss associated with the normalization of elevated glucose and lipid levels, (2) a large individual variability in total nitrogen loss determined principally by the initial lean body mass, and (3) progressive increments in the contribution of fat to weight loss with stable caloric requirements and no evidence of a hypometabolic response.