Effects of plant-based diets on markers of insulin sen-sitivity: A systematic review and meta-analysis of ran-domised controlled trials

Abstract: The aim of this systematic review and meta-analyses was to examine the effects of plant-based diets on markers of insulin sensitivity in people with overweight/obesity, prediabetes, or type 2 diabetes. A systematic literature search in MEDLINE, Embase, CINAHL, and CENTRAL was conducted, and randomised controlled trials (RCTs) investigating the effect of plant-based di-ets (vegan, ovo-vegetarian, lacto-vegetarian, and lacto-ovo-vegetarian) for ≥14 days on markers of insulin sensitivity in adults (≥18 years) with BMI≥25 kg/m2), prediabetes, or type 2 diabetes were eligible. We identified 8 RCTs in-cluding 716 participants. In comparison with control diets, plant-based diets improved Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) (-0.97, 95% confidence interval (CI) (-1.67, -0.27), p=0.007) and fasting insulin (-4.13 µU/ml, 95% CI (-7.22, -1.04), p=0.009) in people with overweight/obesity. In people with prediabetes, one study compared vegan and vegetarian diets, and found no difference in HOMA-IR and fasting insulin. One study in people with type 2 diabetes reported no difference in immunoreactive insulin and metabolic clearance of glucose compared to a conventional diabetes diet. In conclusion, we found that adhering to plant-based diets for at least 14 days im-proved HOMA-IR and fasting insulin in people with overweight/obesity. The number of studies available for the meta-analyses was small, and therefore further well-conducted long-term RCTs with gold-standard measures of insu-lin sensitivity are needed to determine whether a plant-based diet can result in prolonged improvements in insulin sensitivity in people with over-weight/obesity, prediabetes, or type 2 diabetes.