A study conducted on a small number of men concluded that the “love hormone” oxytocin may reduce appetite, helping men lose weight.

Oxytocin – the so-called love hormone. Image via Nauka.

Oxytocin is a hormone existing only in mammals, produced by the hypothalamus and stored and secreted by the posterior pituitary gland. Recent studies have begun to investigate oxytocin’s role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, and maternal behaviors. Most recently, oxytocin has been linked with sobriety from alcohol intoxication. For this reason, it is sometimes referred to as the “bonding hormone” or the “love hormone”.

This new study gave men oxytocin in the form of a nasal spray to see if it can help them lose weight.

“We are seeing early signs that oxytocin reduces how much food someone eats at a meal and improves the way their body handles blood sugar,” said study lead author Dr. Elizabeth Lawson, assistant professor of medicine at Harvard Medical School in Boston.

However, despite the conclusive results of the study, I’d advise maintaining a healthy dose of skepticism, as the research was conducted only on 25 men. The men (12 of which were overweight or obese) had an average age of 27 years; they were asked to self-administer the oxytocin nasal spray one hour before breakfast, and then they were given twice as much food as they ordered.

During the double-blind, controlled, crossover study, the food intake was measured and calories and fat consumption was evaluated. The group was re-tested after two weeks, and the scientists report that people who used the spray significantly reduced their food and calorie intake compared to the control group. Study lead investigator Elizabeth Lawson, MD, assistant professor of medicine at Massachusetts General Hospital and Harvard Medical School in Boston, said:

“We studied the effect of a single dose of oxytocin on food intake and metabolism on healthy men. We are seeing early signs that oxytocin reduces how much food someone eats at a meal and improves the way their body handles blood sugar.”

The research team said that with reduction in calorie and fat intake, oxytocin nasal spray could help in weight loss up to 9 pounds (4 kg) over 12 weeks or 35 pounds (16kg) over a year.  However, it’s quite unlikely that this medication would be used as an effective weight-loss strategy; the monthly cost of administering the spray three times a day would be $275.

Paul Zak, founding director of the Center for Neuroeconomics Studies at Claremont Graduate University in California,  sees potential.

“From an evolutionary perspective, oxytocin is released during positive social interactions — when we are around others who care about us. This is just when food sharing is likely to occur. If we want to lose weight, having others around us who care about us can help reduce appetite,” he suggested.

But there are some significant caveats with this study; first of all, as mentioned above, the small number of study subjects is an issue, and the results have to be replicated over a larger sample size. Manfred Hallschmid, a neuroendocrinologist with the University of Lubeck in Germany is very skeptical of the results:

“Long-term clinical trials are clearly necessary to answer the question whether oxytocin is effective in reducing body weight and if such an effect might go along with unwanted psychosocial side effects.”

It remains to be seen if further studies confirm the potential role of oxytocin in weight loss.

Scientific Reference: Elizabeth Lawson, M.D., assistant professor of medicine, Harvard Medical School, and director, Interdisciplinary Oxytocin Research Program, neuroendocrine unit, Massachusetts General Hospital, Boston; Paul Zak, Ph.D., chairman and professor, economics, and founding director, Center for Neuroeconomics Studies, Claremont Graduate University, Claremont, Calif.; Manfred Hallschmid, Ph.D., neuroendocrinologist, department of neuroendocrinology, University of Lubeck, Germany; March 8, 2015, presentation, Endocrine Society annual meeting,