Introduction: Food habits and wake-sleep cycle influence circadian rhythms. Ramadan fasting (RF) changes food habits and wake-sleep cycle and causes a metabolic imbalance. Melatonin increases sleep quality and daily awareness. The purpose of this study examined the effect of four weeks Ramadan fasting and melatonin supplementation (MS) on sleep quality, melatonin levels and growth hormone (GH) to cortisol ratio in male athletes. Methods: Thirty active men (20-25 years) were randomly divided into supplement (n=15) and placebo (n=15) groups. Body fat percentage and hormones (melatonin, growth hormone, cortisol and growth hormone-cortisol ratio) were evaluated in three times: before the month, mid fasting and post fasting. Blood samples collected at three times; before sleep, wake up time for Sahur and morning wake up time. To evaluate the intervention effect of supplement and sleep conditions on the dependent variable Repeated Measure (factorial 3*3*2) and Bonferroni post hoc tests were used. Results: Melatonin (P=0.001), GH (P=0.001), GH-cortisol ratio (P=0.001) significantly increased in supplement group compare to placebo group. Also, Cortisol (P=0.003) and body fat percentage (P=0.001) decreased in the supplement group compare to placebo group. Sleep quality significantly improved in the supplement group (P=0.025). Conclusion: Supplementing melatonin with improved anabolic conditions and regulated wake-sleep cycle can help the Ramadan fasting condition and prevent the decreased performance during Ramadan fasting.

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