A vegan diet improves insulin resistance in individuals with obesity: a systematic review and meta-analysis

Background A vegan diet has benefits on weight reduction and on the parameters of glucose and lipid metabolism. This meta-analysis aimed to investigate the efficacy of plant-based diets on insulin resistance and blood lipids in patients with obesity. Methods PubMed, Embase, and the Cochrane Library were searched for available papers published up to March 2021. The primary outcome was insulin resistance which was assessed by Homeostasis Model Assessment Insulin Resistance (HOMA-IR), other metabolic parameters measures including the pre/post-diet changes in triglycerides, HDL-cholesterol, total cholesterol, LDL-cholesterol. All analyses were performed using the random-effects model. Results Six studies (seven datasets) were included. Compared with baseline, the plant-based diet improved the HOMA-IR (SMD = 1.64, 95%CI 0.95, 2.33; I 2 = 91.8%, P heterogeneity < 0.001), total cholesterol (SMD = 2.51, 95% CI 0.88, 4.13; I 2 = 98.0%, P heterogeneity < 0.001), HDL-cholesterol (SMD = 1.55, 95% CI 0.66, 2.44; I 2 = 92.0%, P heterogeneity < 0.001), and LDL-cholesterol (SMD = 2.50, 95% CI 1.30, 3.70; I 2 = 94.4%, P heterogeneity < 0.001), but not the triglycerides (SMD = − 0.62, 95% CI − 1.92, 0.68; I 2 = 97.8%, P heterogeneity < 0.001). The sensitivity analyses showed that the results were robust. Conclusions In obese individuals with insulin resistance, a vegan diet improves insulin resistance and dyslipidemia, except for triglycerides.