MELATONIN & SLEEP: SCIENCE-BACKED, PLAIN-LANGUAGE GUIDE “Weight is shaped by sleep–appetite–activity, not one supplement.” There is no clear mechanism that makes melatonin inherently “fattening.” However, sleep affects appetite hormones, glucose regulation, and late-night snacking, so indirect effects are possible. People who sleep better may snack less and move more, supporting weight control. Conversely, if melatonin is taken at the wrong time and causes morning grogginess, reduced daytime activity could make weight management harder. When weight gain occurs, the more common drivers are short sleep, chronic stress, mood issues, nighttime high-calorie eating, or metabolic/hormonal factors—melatonin is often not the primary cause. If you notice increased appetite, daytime fatigue, or reduced motivation after taking melatonin, reassess dose and timing. Also avoid the trap of “I took melatonin, so I can stay up later,” which undermines sleep and weight goals. The best use is a plan that improves sleep rhythm and leaves you more energized the next day.