Abstract
Introduction: In the scenario of chronic non-communicable diseases, there are more than 2.2 billion overweight and obese people in the world. Brazil has an estimated population of more than 20.0 million people in 2025. Studies show that a reduction of around 10.0% in weight also favors the reduction of type 2 diabetes mellitus (T2DM). The imbalance in sleep patterns and the consequent decrease of melatonin (MEL) concentrations in the human body have a major impact on health with the development, mainly of obesity and T2DM. Objective: It was to present the main clinical results of the functions of melatonin in mitigating the comorbidities of obesity and type 2 diabetes mellitus. Methods: The systematic review rules of the PRISMA Platform were followed. The research was carried out from May to June 2024 in the Web of Science, Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: 182 articles were found. A total of 35 articles were evaluated in full and 28 were included and developed in the present systematic review study. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 35 studies with a high risk of bias and 32 studies that did not meet GRADE and AMSTAR-2. Most studies showed homogeneity in their results, with X2=77.8%>50%. It was concluded that melatonin is an important participant in the regulation of energy metabolism, including body weight, insulin sensitivity, and glucose tolerance. Randomized placebo-controlled clinical studies have shown that daily melatonin consumption can be effective in controlling blood pressure, including systemic blood pressure, mean arterial pressure and pulse pressure, and reduces anthropometric indices of obesity in patients, as it increases mass and activity of brown adipose tissue, functioning as an antiobesogenic hormone. Melatonin can regulate adipose tissue and adipokines, such as adipocyte lipolysis, and fat deposition. Furthermore, melatonin can interact with intracellular molecules, acting as an effective antioxidant. Several studies have pointed to a greater risk of developing obesity in people who sleep less than six hours a day. The hormonal changes that occur during sleep deprivation may explain the increase in caloric intake and decrease in leptin, increase in ghrelin and peptide YY. Melatonin also regulates food intake by regulating the production and secretion of insulin, glucagon, and cortisol. Epidemiological studies have shown a link between sleep deprivation, insulin resistance, and T2DM.