SIGNIFICANCE: 39.6% of American adults and 18.5% of young people are obese. Brazil ranks fifth in the world ranking, with about 18 million people. In this scenario, melatonin has evidenced an important function in the regulation of energy metabolism.
INFORMATION GAP: What is the real influence of melatonin supplementation on obesity control?
OBJECTIVE: A systematic review followed by a meta-analysis of randomized clinical trials over the past ten years to explore the efficacy and safety of melatonin for weight reduction and improves of metabolic disorder.
METHODS: The PRISMA rules and COCHRANE INSTRUMENT were followed. The descriptors "melatonin, obesity, metabolism, weight loss, and clinical trial" were used.
RESULTS:  The results (n = 51) were significant that the imbalance of melatonin can lead to metabolic disorders and circadian rhythmic disorders, p <0.05 (R2 = 94.5%). Also, the studies showed improvement in metabolic disorder, glucose homeostasis, weight loss (> 3.0 kg/month), reduced inflammatory process, and improved sleep after supplementation with or without associated drug melatonin. However, it is not yet known the best concentration to be used in humans, especially in the long-term.
                                        General clinical data of the literary findings analyzed