If you have sex frequently, you'll likely stay slim – but not for the reason you suspect.

It's only partly about all that exercise beneath the sheets.

Sex – which only burns about 100 calories an hour – triggers the release of a hormone known as oxytocin. Sometimes referred to as the “cuddle hormone,” oxytocin is a peptide produced in the brain that appears designed to induce feelings of trust and affection. One study even found that men in relationships given a burst of oxytocin spray stood farther away from an attractive woman than men who weren't given any oxytocin. There was no effect on single men, which seemed to indicate that oxytocin may work as a fidelity reinforcer for men who are already bonded with another woman. In women, it actually enables maternal behavior.

But a new study out of York University in Canada indicates that oxytocin is responsible for more than just monogamy. It will actually decrease your appetite – specifically for carbohydrates. The study is the first to demonstrate that variants of the oxytocin receptor (OXTR) gene contribute to why some of us overeat or engage in episodes of binge eating. The researchers investigated how the OXTR gene influences appetite, food preferences, food intake and personality risk traits associated with brain-reward mechanisms.

Over the past decade, lead researcher Dr. Caroline Davis and her team assessed a large group of participants ranging in age from 27 to 50 years. The group had a broad range of body weights and included a substantial number with binge-eating habits. Among other measures, a blood sample was collected from each participant in order to analyze their DNA, the molecules that carry each individual’s unique genetic information.

The DNA analysis uncovered a new link between oxytocin and behaviors associated with binge eating. The researchers focused on seven sites in the DNA where chemical instructions for making OXTR could vary between individuals. These “single nucleotide polymorphisms” (SNPs) were already suspected to be associated with psychological traits. The researchers collected questionnaires about their participants’ differences in reward sensitivity, punishment sensitivity, sugar/fat food preferences, and overeating habits, to be correlated with the OXTR genetic information.

The researchers tested the prediction that these SNPs relate to psychological risk factors, which in turn are associated with overeating behaviors. “Three SNPs were significantly related to the psychological traits, which collectively accounted for 37 percent of the variance in overeating,” says Davis. “Another SNP was directly related to overeating. These results support the role of genes in giving rise to traits that regulate behavior, and highlight the importance of oxytocin in overeating.”

These findings will be presented at the 2016 Annual Meeting of the Society for the Study of Ingestive Behavior, the society for the research into all aspects of eating and drinking behavior.