Role of Melatonin in Body Weight: A Systematic Review and Meta-Analysis

Background: Some trials on animals and human claim that melatonin can influence body weight. So we conducted a systematic review of controlled trials of melatonin effects on weight of human subjects. Methods: First we performed a systematic and comprehensive search in June 2015 on MEDLINE/PubMed, Scopus, Google scholar, hand searching in key journals, the list of references of selected articles and gray literature. Results: We included 7 clinical trials with a total of 244 patients. All studies were parallel clinical trials conducted at the clinic. Evaluating standardized mean difference (SMD) using Cohen's method shows that none of the included studies have found a strong and significant effect of melatonin on body weight. However, some have reported decreasing or increasing effect of melatonin on body weight. We pooled SMDs using random effects (DerSimonian and Laird). Pooled SMD was still not significant SMD (95% CI) = 0.09(-0.17-0.34), with lack of heterogeneity I2=0.0%, p=0.66. Conclusion: We concluded that once the standard treatment had increasing effect on body weight, melatonin could be able to slightly diminish this effect and vice versa. Subgroup analysis showed that melatonin was more effective in child and adolescents. According to the results hypothesis of the buffering role of melatonin on body weight fluctuations can be proposed.