Effects of low-fat diet on serum lipids in premenopausal and postmenopausal women: a meta-analysis of randomized controlled trials.

Objective: This study aims to conduct a meta-analysis to evaluate the effects of a low-fat diet, in comparison with participants' usual diet, on serum lipids in premenopausal and postmenopausal women.

Methods: Ten electronic databases were searched for relevant articles reporting randomized controlled trials through August 31, 2012, including PubMed/Medline, EMBASE, Cochrane Library, CINAHL, Web of Science, SCOPUS, ProQuest Dissertations and Theses, SinoMed, CNKI (Chinese database), and WanFang (Chinese database). This systematic review and meta-analysis, which evaluated the effects of a low-fat diet, in comparison with the participants' usual diet, was conducted according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions. All analyses were performed using RevMan version 5 (Cochrane Collaboration).

Results: From 512 potentially relevant publication citations reviewed, 8 randomized clinical trials were included in the meta-analysis, representing 22 groups (11 intervention groups and 11 control groups). A total of 1,536 women (900 in the intervention group and 636 in the control group) met the inclusion criteria. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) values changed more favorably in participants randomized to low-fat diets than in participants randomized to their usual diets. Low-fat diet was found to induce significant reductions in TC (random-effects model: mean difference [MD], -0.49 mmol/L; 95% CI, -0.69 to -0.29; I = 42%; Peffect < 0.00001), HDL-C (MD, -0.12 mmol/L; 95% CI, -0.20 to -0.05; I = 49%; Peffect = 0.00006), and LDL-C (MD, -0.24 mmol/L; 95% CI, -0.38 to -0.09; I = 42%; Peffect = 0.001) for two groups. For subgroup analysis, low-fat diet was efficacious in reducing TC, HDL-C, and LDL-C in premenopausal women but did not significantly reduce the same outcomes in postmenopausal women. However, there were also no statistically significant differences in triglycerides (TG) and TC-to-HDL-C ratio between a low-fat diet and the participants' usual diet (TG: MD, 0.04 mmol/L; 95% CI, -0.02 to 0.11; I = 0%; Peffect = 0.16; TC-to-HDL-C ratio: MD, 0.08 mmol/L; 95%, CI -0.21 to 0.36; I = 0%; Peffect = 0.59) in two groups.

Conclusions: Overall results suggest that a low-fat diet is efficacious in reducing the concentrations of TC, HDL-C, and LDL-C but not in reducing TG and TC-to-HDL-C ratio in women. A low-fat diet is efficacious in reducing TC, HDL-C, and LDL-C in premenopausal women. Additional studies are needed to further address its effects on postmenopausal women.