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

Abstract

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; I² = 91.8%, P_{heterogeneity} < 0.001), total cholesterol (SMD = 2.51, 95% CI 0.88, 4.13; I² = 98.0%, P_{heterogeneity} < 0.001), HDL-cholesterol (SMD = 1.55, 95% CI 0.66, 2.44; I² = 92.0%, P_{heterogeneity} < 0.001), and LDL-cholesterol (SMD = 2.50, 95% CI 1.30, 3.70; I² = 94.4%, P_{heterogeneity} < 0.001), but not the triglycerides (SMD = - 0.62, 95% CI - 1.92, 0.68; I² = 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.

Keywords: Insulin resistance; Meta-analysis; Obesity; Type 2 diabetes mellitus; Vegan diet.

Fig. 1

Flow diagram of the literature search and filtering results for a systematic review of the effectiveness of a plant diet on obesity

Fig. 2

Forest plot illustrating the impact of plant diet on the metabolic parameter of HOMA-IR in obese patients

Fig. 3

Forest plot illustrating the impact of plant diet on the metabolic parameter of total cholesterol in obese patients

Fig. 4

Forest plot illustrating the impact of plant diet on the metabolic parameter of HDL-cholesterol in obese patients

Fig. 5

Forest plot illustrating the impact of plant diet on the metabolic parameter of LDL-cholesterol in obese patients

Fig. 6

Forest plot illustrating the impact of plant diet on the metabolic parameter of triglycerides in obese patients