Staying up late at night can lead to an additional 2 pounds a month weight gain, researchers reported. The study showed that people who go to bed late eat more food, have worse diets and are more likely to have a higher body mass index.

Many studies over the last 10 years have pointed to the need for people to sleep when they're supposed to (at night) and to sleep for the needed amount of time — about eight hours for adults. Keeping a healthy sleep schedule allows the body's circadian rhythms to stay in sync and keeps a range of metabolic and physiological systems running smoothly.

The study, published online in the journal Obesity, adds to the sleep-weight connection. Northwestern University scientists examined 52 adults on their sleep and dietary patterns. More than half of the participants were normal sleepers — meaning that the midpoint of sleep occurred at or before 5:30 a.m. Late sleepers (44 percent of the sample) got less sleep and went to sleep later.

Late sleepers consumed more calories at dinner and after 8 p.m., ate more fast food, drank more high-calorie soft drinks and had lower fruit and vegetable consumption.