Meta-Analysis of Experimental Studies of the Effect of Melatonin Monotherapy on Body Weight Gain and Eating Behavior in Rats on Different Diets

In an earlier meta-analysis, we showed that long-term melatonin administration minimizes diet-induced changes in lipid profiles. The purpose of our present work was to use a meta-analysis to investigate the effect of melatonin monotherapy on body weight gain (BWG) and eating behavior in rats depending on diet. To this end, we conducted a meta-analysis of 43 publications examining the effects of melatonin monotherapy on BWG, leptin levels, food and water intake in rats fed a standard diet (37 publications), as well as high-fructose diets (5 publications) and fats (9 publications). Our findings suggest that although melatonin reduced the level of triglycerides, total cholesterol and leptin in rats fed high-fructose and high-fat diets but not those fed a standard diet, melatonin treatment prevented BWG in rats on either diet. Increasing the dose of melatonin did not enhance the effect of therapy with any of the diets studied. We did not obtain convincing evidence that the effect of melatonin depends on the initial body weight and age of rats. On a standard diet, melatonin has been found to reduce food and water intake. Melatonin did not reduce BWG with a standard diet when administered intraperitoneally. Our research suggests that melatonin may be beneficial for diet-induced metabolic disorders by improving lipid profiles and preventing BWG. However, a decrease in appetite and BWG when taking melatonin may also be associated with negative side effects of the drug, which requires further research.