Do you keep vampire hours? Are you the type to come alive after midnight, watching TV, maybe talking to other children of the night? If so, keep an eye on your waistline because people who regularly stay up late are at higher risk of weight gain, according to a study published in Obesity and reported in a Northwestern University press release.

For the study, researchers from Northwestern University in Chicago examined 51 people averaging age 30. Of those participants, 23 were late-nighters, going to sleep by 3:45 A.M. and getting up by 10:45 A.M. The remainder were average sleepers who hit the sheets at 12:30 A.M. and were up by 8 A.M.

Scientists found that late-nighters ate 248 more calories daily. And their calorie sources? More fast food and sugary drinks and half as many fruits and veggies than participants with earlier bed times. What’s more, the night owls ate most of their extra calories at dinnertime and later in the evening. They also had a higher body mass index (height to weight ratio) than normal sleepers.

“The extra daily calories can mean a significant amount of weight gain––two pounds per month––if they are not balanced by more physical activity,” said Kelly Glazer Baron, PhD, MPH, a health psychologist and a neurology instructor at Northwestern University Feinberg School of Medicine, and the study’s co-lead author.

The reason behind night owls’ weight gain could be that healthier foods aren’t readily available at night and that these folks simply prefer higher calorie foods, researchers suggested. In addition, scientists concluded, when sleeping and eating habits are not in sync with the body’s internal clock, they change a person’s appetite and metabolism, which might lead to weight gain.

Researchers also stressed that eating unhealthy foods at the wrong time of day increases the risk of stroke, heart disease and gastrointestinal disorders.

Click here to learn how getting satisfactory sleep is linked to people making healthier food choices.