It may seem obvious, but the later you stay up at night and the less sleep you get, the more weight you will gain. A study published in the journal, Sleep, examined 225 individuals and compared those who went to sleep at 4am and woke up at 8 am (getting only 4 hours of sleep) to control subjects.
The study, which was the largest and most diverse sample studied under laboratory conditions, found that sleep restriction promoted weight gain. The results showed that sleep deprived individuals consumed 550 extra calories after 11pm. These calories were mostly from fat, resulting in an average of an extra 2.2 pounds after 5 nights of limited sleep. As a whole, the sleep deprived group ate more times throughout the day, eating less in the morning and shifting their caloric intake toward the nighttime. The study also found racial differences; African American men gained the most weight, about 3.7 pounds.
There are many theories as to why people gain weight with sleep loss, but we do not know the exact reason. It may be related to abnormal levels of hormones that regulate food intake, or because control centers in the brain are weakened with sleep loss. It is very important to get adequate sleep and to avoid eating within 2 hours of going to bed in order to maintain your weight and general overall health.