Effect of energy restriction, weight loss, and diet composition on plasma lipids and glucose in patients with type 2 diabetes

OBJECTIVE: To determine the optimal diet for improving glucose and lipid profiles in obese patients with type 2 diabetes during moderate energy restriction. RESEARCH DESIGN AND METHODS: A total of 35 free-living obese patients with type 2 diabetes were assigned to one of three 1,600 kcal/day diets for 12 weeks. The diets were high carbohydrate (10% fat, 4% saturated), high monounsaturated fat (MUFA) (32% fat, 7% saturated), or high saturated fat (SFA) (32% fat, 17% saturated). RESULTS: Diet composition did not affect the magnitude of weight loss, with subjects losing an average of 6.6 +/- 0.9 kg. Energy restriction and weight loss resulted in reductions in fasting plasma glucose (-14%), insulin (-27%), GHb (-14%), and systolic (-7%) and diastolic blood pressure (-10%) levels and the glucose response area (-17%) independent of diet composition. Diet composition did affect the lipoprotein profile. LDL was 10% and 17% lower with the high-carbohydrate and high-MUFA diets, respectively, whereas no change was observed with the high-SFA diet (P < 0.001 for effect of diet). HDL was transiently reduced on the high-carbohydrate diet at weeks 1, 4, and 8, whereas higher fat consumption maintained these levels. The total cholesterol:HDL ratio, although significantly reduced on the high-MUFA diet (P < 0.01), was not different from the other two diets after adjustment for baseline differences. CONCLUSIONS: Energy restriction, independent of diet composition, improves glycemic control; however, reducing SFA intake by replacing SFA with carbohydrate or MUFA reduces LDL maximally during weight loss and to a greater degree than has been shown in weight-stable studies.L K Heilbronn, M Noakes and P M Clifto