Meta-Analysis of Experimental Studies of Diet-Dependent Effects of Melatonin Monotherapy on Body Weight Gain and Eating Behavior in Rats

In a previous meta-analysis, we showed that long-term melatoninadministration minimizes diet-induced changes in lipid profiles.The present work was aimed to use a meta-analysis to study the diet-denendenteffect of melatonin monotherapy on body weight gain (BWG) and eatingbehavior in rats. We carried out a meta-analysis of 43 publicationsexamining the effects of melatonin monotherapy on BWG, blood leptinlevels, food and water intake in rats fed a standard diet (37 publications),as well as high-fructose (5 publications) and high-fat (9 publications)diets. Our findings suggest that although melatonin reduced triglyceride,total cholesterol and leptin levels in rats fed high-fructose andhigh-fat, but not a standard, diets, melatonin therapy preventedBWG in rats on either diet. Increasing the dose of melatonin didnot enhance the effect of therapy on any diet. We did not obtainconvincing evidence that the effect of melatonin depends on theinitial body weight and age of rats. On a standard diet, melatonin hasbeen found to reduce food and water intake. Melatonin did not reduceBWG with a standard diet when administered intraperitoneally. Ourresearch suggests that melatonin may be beneficial in diet-inducedmetabolic disorders as it improves lipid profiles and prevents BWG.However, a decrease in appetite and BWG when taking melatonin mayalso be due to negative side effects of the drug, which requiresfurther research.