Low glycaemic index and glycaemic load diets in adults with excess weight: Systematic review and meta‐analysis of randomised clinical trials

Abstract Background To compare the effects of low and high glycaemic index/glycaemic load (GI/GL) diets on body weight in adults with excess weight. Methods We searched for randomised controlled trials comparing low GI/GL vs. high GI/GL diets from Medline (via PubMed), Embase, Scopus and Web of Science. The variables of interest were anthropometric measurements, fasting glucose and fasting insulin levels and lipid profile, and 10 studies were included in the meta‐analysis. Results The sample size ranged from 19 to 203 participants. Low GI/GL is not superior to high GI/GL diets on body weight reduction in adults with excess weight (body mass index [BMI] ≥ 25 kg m –2 ). However, low GI/GL diets show greater body weight reductions in adults with BMI ≥ 30 kg m –2 (−0.93 kg; 95% confidence interval [CI] = −1.73 to −0.12; p = 0.045). Compared with high GI/GL diets, low GI/GL diets may also help reduce fasting glucose (−1.97 mg dl –1 ; 95% CI = −3.76 to 0.19; p = 0.030) and fasting insulin (−0.55 µU ml –1 ; 95% CI = −0.95 to –0.15; p = 0.007). No differences in fat mass, fat‐free mass, waist circumference and lipid profile were observed between low GI/GL and high GI/GL diets. The risk of bias for body weight was classified as ‘low risk’ (25% of the studies) and ‘some concerns’ for all domains of RoB 2 tool in most studies. Conclusions When compared with high GI/GL diets, low GI/GL diets appear to more effectively reduce fasting glucose and insulin and promote greater body weight reduction in adults with obesity (BMI ≥ 30 kg m –2 ).