Key Takeaways of Melatonin and Body Composition Article
- Melatonin and body composition improved in one year-long trial of postmenopausal women.
- The melatonin group had 6.9% lower fat mass versus placebo, measured by DXA.
- Body weight and BMI did not change significantly between groups.
- BMI-adjusted lean mass was 2.6% higher with melatonin, but DXA lean mass does not prove muscle growth
- Current evidence does not support melatonin as a stand-alone supplement for fat loss or muscle growth.
Melatonin and Body Composition: What Researchers Did
Melatonin and Body Composition: What Researchers DidMelatonin and body composition may be linked in specific clinical settings, but current evidence does not show that melatonin reliably produces fat loss or muscle growth in healthy lifters.
The best direct evidence comes from postmenopausal women, not young adults following progressive resistance-training programs. Therefore, the study offers a signal worth understanding—not a new supplement rule.
What happened to fat mass and lean mass?
The 2016 Melatonin Study: What Researchers Did
In Clinical Endocrinology, Anne Kristine Amstrup and colleagues (2016) conducted a randomized, double-blind, placebo-controlled trial in 81 postmenopausal women.
Participants received 1 milligram or 3 milligrams of melatonin nightly, or placebo, for one year. Researchers measured body composition using dual-energy X-ray absorptiometry, commonly called DXA (Amstrup et al., 2016).
| Outcome | Melatonin finding versus placebo |
|---|---|
| Fat mass | 6.9% lower. |
| Lean mass | 2.6% higher after BMI adjustment |
| Body weight and BMI | No significant between-group differences |
The study directly supports the outcomes in this table, but it does not establish why the changes occurred.
Melatonin and Body Composition: What the Fat-Loss Result Means
The most striking result was the lower fat mass in the melatonin group. However, the finding was a between-group difference in DXA-estimated fat mass, not proof that melatonin is an effective fat-loss tool in broader populations.
The same trial found no significant group difference in body weight or BMI. That matters because meaningful fat loss usually shows up in at least some combination of body mass, circumference, or repeated body-composition measures.
A 2024 meta-analysis of 28 randomized trials involving 1,543 adults found no significant pooled effect on body weight, BMI, or waist circumference. It did report a 1.21-centimeter reduction in hip circumference, but it did not pool DXA-derived fat mass or lean mass outcomes (Vajdi et al., 2024).
A newer review focused on menopausal women likewise found no significant pooled improvement in BMI. Its authors concluded that the evidence remains inconclusive for BMI and several other outcomes in this population (Du & Tan, 2026).
Melatonin and Body Composition: Does Lean Mass Mean More Muscle?
No—at least not based on this trial.
DXA “lean mass” includes skeletal muscle, but it also includes water, organs, connective tissue, and other non-fat tissue. Amstrup et al. did not measure muscle-fiber size, muscle protein synthesis, strength gains, or resistance-training performance (Amstrup et al., 2016).
That means the study cannot support claims about melatonin for muscle growth. A separate athlete trial measured markers of oxidative stress and muscle damage after 100 mg per day of melatonin for four weeks, not hypertrophy or strength progress (Leonardo-Mendonça et al., 2017).
The dose in that athlete study was also far above the 1–3 mg nightly dose used by Amstrup and colleagues. These studies answer different questions and should not be combined into a muscle-building claim.
Why Melatonin in Postmenopausal Women May Be Different
The 2016 trial involved postmenopausal women, a group in which sleep, hormonal changes, bone health, and body-composition changes can overlap.
A 2021 systematic review of 24 studies and 1,173 participants found that melatonin research in menopausal women covers many outcomes, including sleep, bone health, BMI, and menopausal symptoms. However, the review did not establish consistent evidence for melatonin’s effects on glucose-related measures (Treister-Goltzman & Peleg, 2021).
Earlier randomized research in perimenopausal and menopausal women also examined hormone and mood outcomes rather than DXA body composition (Bellipanni et al., 2001).
Mechanism research gives melatonin a plausible connection to metabolism and energy balance, but much of that work comes from animal models. Plausible biology is not the same as confirmed fat loss in humans (Owino et al., 2019).
Why the mechanism is still uncertain
Melatonin has plausible biological roles in circadian rhythm regulation, oxidative stress, glucose regulation, and energy metabolism. However, plausible is not the same as proven in humans.
Mechanistic reviews discuss melatonin receptors, adipose tissue, glucose regulation, and energy balance. Yet much of the encouraging research comes from animal or laboratory studies, which cannot establish that a supplement will produce the same physique outcomes in humans (Owino et al., 2019).
In other words, melatonin may affect metabolic pathways. That does not prove it causes meaningful fat loss in people who lift.
Practical applications for lifters and coaches
If you are considering melatonin for fat loss, keep the hierarchy straight:
- Use training, nutrition, and sleep consistency as your primary body-composition tools.
- Treat melatonin as a sleep-timing supplement—not a fat burner.
- Do not assume the study’s lean-mass result means more muscle tissue or better hypertrophy.
- Remember that the main trial involved postmenopausal women, so its findings may not apply to younger, active lifters.
- If you use melatonin regularly or take medication, talk with a qualified healthcare professional first.
For building muscle, prioritize progressive resistance training, enough total calories, and adequate protein. For many lifters, that means roughly 0.7–1.0 grams per pound (1.6–2.2 g/kg) of protein daily, adjusted for goals and total diet.
Conclusion: is melatonin useful for body composition?
Melatonin and body composition may be linked in certain populations, but the evidence is not strong enough to call melatonin a fat-loss or muscle-growth supplement.
Amstrup et al. (2016) found lower DXA fat mass and higher BMI-adjusted lean mass after one year in postmenopausal women. Yet there was no significant change in body weight or BMI, and later pooled evidence did not show consistent overall effects on those outcomes (Vajdi et al., 2024).
Use melatonin for sleep only when it is appropriate for you. Build your physique with training, nutrition, recovery, and consistency.
FAQ
Can melatonin help with body fat loss?
Melatonin and body composition research does not show that melatonin reliably causes body-fat loss. One trial found lower DXA-measured fat mass in postmenopausal women, but the largest available meta-analysis found no significant overall effect on body weight, BMI, or waist circumference (Amstrup et al., 2016; Vajdi et al., 2024).
Does melatonin build muscle?
Melatonin for muscle growth is not supported by direct hypertrophy research. The main body-composition trial measured lean mass with DXA, not muscle-fiber growth, muscle protein synthesis, or strength progress. Lean mass can change because of water and other non-fat tissues, not only skeletal muscle (Amstrup et al., 2016).
What dose was used in the 2016 study?
Melatonin and body composition research from Amstrup and colleagues used 1 mg or 3 mg of melatonin nightly for one year. The researchers combined the melatonin groups for the main comparison with placebo (Amstrup et al., 2016).
Is melatonin an antibiotic?
Melatonin and body composition research has no connection to antibiotic treatment. Melatonin is not an antibiotic and cannot treat bacterial infections. Although it has been studied for antioxidant-related actions, that does not make it an infection treatment or explain the 2016 body-composition result.
Does melatonin cause weight loss?
Melatonin for fat loss is not supported as a reliable weight-loss strategy. The 2016 trial found no significant difference in body weight or BMI, and the 2024 meta-analysis also found no significant pooled effect on either outcome (Amstrup et al., 2016; Vajdi et al., 2024).
Why does melatonin research focus on postmenopausal women?
Melatonin in postmenopausal women has been studied because menopause, aging, sleep disruption, and body-composition changes often overlap. Still, these findings cannot automatically be applied to younger adults, men, or resistance-trained populations (Treister-Goltzman & Peleg, 2021).
Medical Disclaimer
This article is for educational purposes only and is not medical advice. Supplements can interact with medications and may not be appropriate for everyone. Consult a qualified healthcare professional before starting or changing a supplement routine.
References
Amstrup, A. K., Sikjaer, T., Pedersen, S. B., Heickendorff, L., Mosekilde, L., & Rejnmark, L. (2016). Reduced fat mass and increased lean mass in response to 1 year of melatonin treatment in postmenopausal women: A randomized placebo-controlled trial. Clinical Endocrinology, 84(3), 342–347. https://doi.org/10.1111/cen.12942
Bellipanni, G., Bianchi, P., Pierpaoli, W., Bulian, D., & Ilyia, E. (2001). Effects of melatonin in perimenopausal and menopausal women: A randomized and placebo controlled study. Experimental Gerontology, 36(2), 297–310. https://doi.org/10.1016/S0531-5565(00)00217-5
Leonardo-Mendonça, R. C., Ocaña-Wilhelmi, J., De Haro, T., et al. (2017). The benefit of a supplement with the antioxidant melatonin on redox status and muscle damage in resistance-trained athletes. Applied Physiology, Nutrition, and Metabolism, 42(7), 700–707.
Owino, S., Buonfiglio, D. D. C., Tchio, C., & Tosini, G. (2019). Melatonin signaling: A key regulator of glucose homeostasis and energy metabolism. Frontiers in Endocrinology, 10, 488. https://doi.org/10.3389/fendo.2019.00488
Toffol, E., Kalleinen, N., Haukka, J., Vakkuri, O., Partonen, T., & Polo-Kantola, P. (2014). Melatonin in perimenopausal and postmenopausal women. Menopause, 21(5), 493–500. https://doi.org/10.1097/GME.0b013e3182a6c8f3
Treister-Goltzman, Y., & Peleg, R. (2021). Melatonin and the health of menopausal women: A systematic review. Journal of Pineal Research, 71(2), e12743. https://doi.org/10.1111/jpi.12743
Vajdi, M., Moeinolsadat, S., Noshadi, N., Pourteymour Fard Tabrizi, F., Khajeh, M., Abbasalizad-Farhangi, M., & Alipour, B. (2024). Effect of melatonin supplementation on body composition and blood pressure in adults: A systematic review and dose-response meta-analysis of randomized controlled trials. Heliyon, 10(14), e34604. https://doi.org/10.1016/j.heliyon.2024.e34604
Walecka-Kapica, E., Klupińska, G., Chojnacki, J., Tomaszewska-Warda, K., Błońska, A., & Chojnacki, C. (2014). The effect of melatonin supplementation on the quality of sleep and weight status in postmenopausal women. Prz Menopauzalny, 13(6), 334–338. https://doi.org/10.5114/pm.2014.47986
