Short-term effects of a high-fiber, high-carbohydrate diet in very obese diabetic individuals.

The short-term effects of a weight-maintenance diet high in fiber and carbohydrate (HFHC) was studied in seven very obese individuals with type II diabetes mellitus. Such diets contained 68% of kcal as carbohydrate and total fiber content of 81 g (in contrast to 42% and 28 g during baseline). Fasting glucose concentrations, summed glucose concentrations, and 24-h glucosuria were unaffected in six of seven individuals. Fasting insulin levels decreased (-6.0 +/- 2.0 microU/ml, P less than 0.05), but meal-stimulated insulin concentrations were not altered. Triglyceride and HDL cholesterol concentrations were also unaffected. Total cholesterol concentrations fell in four individuals whose initial values exceeded 200 mg/dl. Basal glucose production rates were similar in the obese diabetic subjects, in five nonobese normal subjects, and in one obese normal individual (2.05 +/- 0.19 versus 2.63 +/- 0.30 and 1.85 mg/kg/min for the obese normal individual) while on baseline diets, and did not change with HFHC. During isoglycemic hyperinsulinemic glucose clamp procedures (maintenance of basal glucose concentrations), 40 mU/m2/min was infused intravenously for 2 h. Glucose disappearance rates increased significantly in the normal-weight control subjects, but did not increase during baseline diets in the obese type II diabetic subjects (4.65 +/- 0.80 versus 0.68 +/- 0.40 mg/kg/min). HFHC diet had no effect on glucose disappearance rates. Plasma insulin levels were 131.0 +/- 11.0, 120.0 +/- 11.0, and 120.0 +/- 5.0 microU/ml during these studies. These studies indicate that short-term HFHC diets without caloric restriction were ineffective in improving glycemic control or lessening insulin resistance in very obese patients with type II diabetes.