Low-fat diet vs high-monounsaturated fat diet and type 2 diabetes

Nutrition Research Newsletter, Sept, 2004

The most striking finding in this study was that the ad libitum low-fat, high-fiber diet induced a significant weight loss, whereas the high-mono diet did not. Body weight decreased >1.0 kg in 8 of the 11 participants during the low-fat diet and in only 3 of the 11 subjects during the high-mono diet. The subjects were offered a mean of 3555 kcal/d during both diets, which is 25% above the eucaloric energy requirement of 2848 [ or -] 281 kcal/d. The subjects consumed 212 fewer kcal per day during the low-fat diet than during the high-mono diet.

Plasma total, LDL-, and HDL-cholesterol concentrations decreased from both diets. Both diets lowered the mean plasma LDL-cholesterol concentration to <100 mg/dL, which is the treatment goal for diabetic patients. Mean plasma triacylglycerol and VLDL-cholesterol concentrations did not change significantly during either diet. The triacylglycerol responses of some subjects were of interest, however--particularly those of the subject with the highest baseline plasma triacylglycerol concentration (639 mg/dL). In that subject, the fasting plasma triacylglycerol concentration decreased substantially and similarly during both diets (40.0% during the low-fat diet and 38.6% during the high-mono diet). There were no significant differences in the ratios of plasma LDL to HDL cholesterol or of total to HDL cholesterol. Plasma glucose, fructosamine, and Hb A1c concentrations and glucose infusion rates during the hyperinsulinemic, euglycemic clamp studies did not differ between the 2 diets.

The unique feature of this study was that an ad libitum low-fat, high-complex carbohydrate diet caused weight loss in type 2 diabetes patients, whereas an ad libitum high-mono diet did not lead to weight loss. The low-fat diet did not cause the plasma triacylglycerol concentrations to increase and did not worsen glycemic control, contrary to past studies in which "eucaloric" low-fat diets were prescribed to maintain body weight. A particularly important result of this study was that the low-fat diet did not worsen the fasting plasma lipid and lipoprotein profile. It is important that plasma triacylglycerol concentrations did not increase during the low-fat diet. Another finding is that glycemic control did not deteriorate during the low-fat diet. This result stands in contrast to previous reports that low-fat, high-carbohydrate diets may cause a deterioration in glycemic control in type 2 diabetes.

In summary, an ad libitum, low-fat, high-fiber, high-complex carbohydrate diet resulted in greater weight loss than did a high-mono diet, and the former did not increase plasma triaeylglycerol concentrations from baseline or worsen glycemic control in patients with type 2 diabetes mellitus. Long-term consumption of a low-fat diet might be associated with even greater weight loss and additional improvement of plasma lipid concentrations.

G Gerhard, A Ahmann, K Meeuws, M McMurry, P Barton Duell, W Connor. Effects of a low-fat diet compared with those of a high-monounsaturated fat diet on body weight, plasma lipids and lipoproteins, and glycemic control in type 2 diabetes. Am J Clin Nutr 80(3):668-673 [Correspondence: WE Connor, Department of Medicine, L465 Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098. E-mail: connorw@ohsu.edu]