Effects of moderate (MF) versus lower fat (LF) diets on lipids and lipoproteins: a meta-analysis of clinical trials in subjects with and without diabetes

Background: Dyslipidemia increases coronary heart disease (CHD) risk and often presents in diabetes, which amplifies risk of CHD. Lower fat (LF) diets increase triglyceride (TG) and decrease high-density lipoprotein cholesterol (HDL-C); moderate fat (MF) diets decrease TG and lower HDL-C less. Objective: To quantify the magnitude of lipid and lipoprotein responses to MF versus LF cholesterol-lowering weight maintenance diets in subjects with and without diabetes. Methods: A meta-analysis of 30 controlled-feeding studies (n = 1213 subjects) was conducted to evaluate LF versus MF diets on lipids and lipoproteins in subjects with and without diabetes. Results: In all subjects, MF and LF diets decreased low-density lipoprotein cholesterol (LDL-C) similarly. MF diets decreased HDL-C less versus LF diets. The estimated increase in HDL-C after MF diets versus LF diets was 2.28 mg/dL (95% confidence interval 1.66 to 2.90 mg/dL, P < .0001). MF diets decreased TG, whereas LF diets increased TG. The decrease in TG was -9.36 mg/dL (-12.16 to -6.08 mg/dL, P < .00001) for MF versus LF diets. In subjects with diabetes, there was a similar increase in HDL-C (2.28 mg/dL) versus subjects without diabetes; however, there was a greater reduction in TG (-24.79 mg/dL, P < .05) on the MF diet. Subjects with diabetes had greater reductions in the total cholesterol (TC) to HDL-C ratio (TC:HDL-C) (-0.62, P < .0001) and non-HDL-C (-5.39 %, P < .06) after MF versus LF diets. Conclusions: Both men and women had greater estimated reductions (6.37% and 9.34%, respectively) in predicted CHD risk after MF diets compared to LF diets. Moreover, based on greater reductions in TG, the TC:HDL-C ratio and non-HDL-C in subjects with diabetes, the CHD risk reduction would be greater for a MF versus a LF weight maintenance, cholesterol-lowering diet.