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.
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.
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.”
Reduced fat mass and increased lean mass in response to 1 year of melatonin treatment in postmenopausal women: A randomized placebo-controlled trial.
Apart from regulating the circadian rhythm, melatonin exerts a variety of actions in the living organism. Among these functions, melatonin is believed to have a positive effect on body weight and energy metabolism. So far, the evidence for this relies mainly on animal models. In this study, we aimed to determine the effects of melatonin on body composition, lipid and glucose metabolism in humans.
In a double-blind, placebo-controlled study, we randomized 81 postmenopausal women to 1 year of treatment with melatonin (1 or 3 mg nightly) or placebo. Body composition was measured by DXA. Measures were obtained at baseline and after 1 year of treatment along with leptin, adiponectin and insulin. Markers of glucose homeostasis were measured at the end of the study.
In response to treatment, fat mass decreased in the melatonin group by 6·9% (95% CI: 1·4%; 12·4%, P = 0·02) compared to placebo. A borderline significant increase in lean mass of 5·2% was found in the melatonin group compared to placebo (3·3%, (IQR:-1·7; 6·2) vs -1·9%, (IQR: -5·7; 5·8), P = 0·08). After adjusting for BMI, lean mass increased by 2·6% (95% CI: 0·1; 5·0, P = 0·04) in the melatonin group. Changes in body weight and BMI did not differ between groups. Adiponectin increased borderline significantly by 21% in the melatonin group compared to placebo (P = 0·08). No significant changes were observed for leptin, insulin or markers of glucose homeostasis.
Our results suggest a possibly beneficial effect of melatonin on body composition and lipid metabolism as 1 year of treatment reduces fat mass, increases lean mass and is associated with a trend towards an increase in adiponectin.
© 2015 John Wiley & Sons Ltd.
PMID: 26352863 DOI: 10.1111/cen.12942 [PubMed – in process]