A new study in the Proceedings of the National Academy of Sciences now confirms previous theories that being on the night shift is actually an occupational hazard. The findings show that circadian disruption, when a person’s circadian rhythms split off from the regular day-night cycle, cause key metabolic hormones to act crazy.

For instance: When your body’s no longer sleeping when it thinks it should be, it stops producing as much leptin, a hormone that signals a body to stop eating. It also releases more cortisol, a stress hormone that’s been linked to high blood pressure and obesity.