Do you like to stay up late and then spend your morning sleeping in? If so, you may be sabotaging your attempts at weight loss. According to a recent study, people who stay up until 3 a.m. and sleep until after 10 a.m. are more likely to eat the bulk of their calories later in the day, consume fewer vegetables and fruits, and eat more fast food when compared to people that go to bed around midnight and wake up by 8 a.m. If your goal is medical weight loss, take heed: when you sleep and eat has a great effect on your weight loss.

In a Northwestern Medicine study, researchers explored the relationship between dietary behavior, body mass index (BMI), and sleeping and waking hours. The study found that “late sleepers” eat 248 more calories per day, half as many vegetables and fruits, and eat twice as much fast food as “early sleepers.” Furthermore, the majority of those extra calories were consumed later in the day, which can equate to weight gain of up to two pounds each month. These findings are significant because it shows that not only are the number of calories consumed important, but also the time of day when the food is eaten. These factors are also linked to the time that you go to sleep and the time that you wake up.

This study calls to light the issue of circadian rhythms of sleep, which are connected to the rotation of the earth and daylight and nighttime. In other words, when it’s dark outside, you’re supposed to be sleeping, not eating. This is true no matter where you live; if you live in Beverly Hills or Bakersfield, California, your circadian rhythms are tied to sunrise and sunset. If eating and sleeping are not aligned with daylight, the result can be significant changes in appetite, metabolism and weight gain. Therefore, if your goal is medical weight loss, it’s important to eat and sleep at the proper times in order to see optimal results.