Effects of dietary macronutrient composition on glycemic control and cardiovascular risk factors  

Dominic N. Reeds, M.D.

Project  Overview:
Obesity is a known risk factor for development of type 2 diabetes. Lifestyle changes consisting of weight loss and regular exercise are important to reduce cardiac risk and improving blood sugar control. The best diet to achieve these changes is unclear however. The American Diabetes Association recommends a weight-losing diet that is composed of approximately 60% of calories from carbohydrate and 15-20% of calories from protein. Surprisingly, other than reduced food intake, this diet composition is very similar to that consumed by the average American. Diets that are higher in protein and lower in carbohydrate may improve blood sugar and cardiac risk more than that of a standard ADA diet. Therefore we will perform an 8 month worksite intervention in which 2 groups of diabetic subjects will receive supervised physical activity and behavioral therapy to cause 8% weight loss. Subjects will be randomized to either receive a diet consistent with current ADA guidelines or a high protein/low carbohydrate diet. We will measure heart function and blood sugar control before and after the intervention in both groups to determine which group had the greatest benefit. This study will determine which diet should be recommended for people suffering from type 2 diabetes.

Progress Report:
Since September 2013, we have identified and telephone-screened 185 potential subjects with Type 2 diabetes. Of these, 156 were excluded after a detailed phone screening, and an additional 15 were excluded after medical screening. The remaining 15 subjects completed baseline testing and were randomized to either the intervention group (Optimum Lifestyle Intervention [OLI]) (n=7) or control group (Standard Care [SC]) (n=7). Two SC subjects withdrew from the study, and a ninth subject will complete baseline testing in early June. There were no statistically significant differences between the groups at baseline. OLI subjects lost 16% of their initial body weight, reduced their liver fat by 80% and despite a 70% dose reduction in anti-diabetic medications with a 10% reduction in hemoglobin A1C. The ability of the body to remove sugar from the blood stream improved by 145% and systolic and blood pressure were reduced by 15mmHg and 9mmHg respectively in the OLI group. There were no changes in the parameters in the SC group. These data strongly suggest that a high-protein, lower carbohydrate diet in conjunction with an intensive lifestyle intervention program produces dramatic improvements in metabolic indicators of cardiovascular and mortality. Reducing the proportion of calories derived from carbohydrate may be advisable in many patients with Type 2 diabetes mellitus.