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A year on melatonin: a couple of kilos less fat and a couple of kilos more lean body mass

Long-term supplementation with a low dose of melatonin reduces fat reserves by a couple of kilograms and increases lean body mass by almost the same amount. Endocrinologists at Aarhus University Hospital in Denmark discovered this after getting women aged 56-73 to take 1 or 3 mg melatonin every evening for a year.


Melatonin is popular among life extensionists. Animal studies have shown that lab mice live longer if you put melatonin in their drinking water, that melatonin delays the aging process in brain cells, and that it prevents the increase of fat reserves as a result of aging.

As more and more people are becoming obese, the Danes were particularly interested in the effects of melatonin on fat mass. It's not precisely known how melatonin inhibits the growth of fat tissue, but in-vitro research has shown that melatonin decreases the activity of the fat receptor PPAR-gamma in fat cells, so they grow less fast. [J Pineal Res. 2010 Nov;49(4):364-72.] [J Pineal Res. 2009 Oct;47(3):221-7.] Melatonin also seems to play an important role in the regulation of the glucose/insulin balance. [Eur J Pharmacol. 2009;606(1-3):61-71.]

So could melatonin help people stay slim? This is the question the researchers set out to answer by doing a human study in which 81 women participated. Before going to sleep the women took either a placebo, a supplement containing 1 mg melatonin or a supplement containing 3 mg melatonin.

All of the women were showing the first signs of osteoporosis and were taking a daily dose of 800 mg calcium and 20 mcg vitamin D3. The researchers also wondered whether melatonin can help strengthen bones.

Regardless of the dose, the women in the melatonin groups lost body fat, whereas the women in the placebo group gained body fat. At the end of the experiment the women who had taken melatonin had lost about 5 percent of their body fat. At the same time the lean body mass of the women in the melatonin groups had increased by more than 3 percent. The study does not reveal to what extent the increase in lean body mass was due to the women's bones becoming heavier or to muscle growth.

A year on melatonin: a couple of kilos less fat and a couple of kilos more lean body mass

A year on melatonin: a couple of kilos less fat and a couple of kilos more lean body mass

The researchers discovered that melatonin supplementation made the women's bodies more sensitive to insulin. The higher the women's BMI, the stronger the effect, as is shown in the figure below.

A year on melatonin: a couple of kilos less fat and a couple of kilos more lean body mass

The increase in insulin sensitivity may have been due to the increase in secretion of adiponectin by the fat cells.

"We demonstrated that small doses of melatonin (1 and 3mg/d) have beneficial effects on body composition in terms of reduced fat mass and borderline significantly increased lean mass in post-menopausal women", the researchers wrote.

"Our findings may be explained by a melatonin-driven increase in osteogenesis resulting in decreased adipogenesis. On the basis of our study, melatonin may be an interesting therapeutic agent for future treatment strategies against osteoporosis and age-related changes in body composition."

Clin Endocrinol (Oxf). 2016 Mar;84(3):342-7.

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