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. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13098-022-00879-w.