Effect of low-carbohydrate diet on adiponectin level in adults: a systematic review and dose-response meta-analysis of randomized controlled trials

Background: To the best of our knowledge, no previous study has reported findings on the effects of low-carbohydrate diet (LCD) on adiponectin concentration. Objective: The current systematic review and dose-response meta-analysis was carried out to systematically review the available controlled clinical trials about the effect of LCD on adiponectin level in adults. Methods: Literature searches of PubMed/Medline, Scopus and Web of Sciences were conducted up to August 2019. Randomized controlled trials (RCTs) which assessed the effect of LCD on the adiponectin level were selected. Results: Eleven studies, including 1047 participants (LCD = 534 and control = 513), were included in the meta-analysis. Proportion of carbohydrate from calorie was from 4 to 34%. Time of the follow-up varied between studies and ranged from 6 to 152 weeks. LCD intake mildly but significantly increased adiponectin (0.02 mu g/ml, 95% CI: 0.01 to 0.03, P < 0.001). Dose-response analysis indicated a nonlinear association between the percentage of carbohydrate and change in adiponectin level from baseline (P = 0.04). After subgroup analysis based on the proportion of carbohydrate from calorie, there was a significant increase in adiponectin concentration in studies that prescribed <30% of calorie from carbohydrates (0.12 mu g/ml, 95% CI: 0.07-0.18). In contrast, diets which consisted >= 30% of carbohydrates had no significant effect on adiponectin (0.50 mu g/ml, 95% CI: -0.46 to 1.48). Also, meta-regression analysis revealed that age (beta = 0.04, P = 0.15), baseline BMI (beta= -0.15, P = 0.15), time of follow-up (beta = 0.01, P = 0.17), percentage of carbohydrates (beta = 0.004, P = 0.90), percentage of protein (beta= -0.12, P = 0.08), percentage of fat (beta = 0.20, P = 0.61) and baseline adiponectin (beta = 0.001, P = 0.97) are not sources of heterogeneity. Conclusion: This systematic review and meta-analysis demonstrated a mild but significant effect of LCD on adiponectin concentration compared to control groups.