Night owls trying to lose weight may want to set an earlier bedtime.
People who go to bed late and sleep in tend to eat more calories in the evening, more fast food and full-calorie soda, and fewer fruits and vegetables than people who are early to bed and early to rise, according to a study published online in the journal Obesity.
These nocturnal habits can increase the risk of weight gain if they aren’t offset by exercise, said the researchers from Northwestern University’s Feinberg School of Medicine.
A calorie is a unit of energy. One that’s eaten at 8 p.m. isn’t any different than one that’s consumed at 1 p.m., as long as activity offsets the energy gain. But sleep and meal timing may be more important than previously thought, the study suggested.
If sleep and eating are not aligned with the body’s internal clock, it may cause changes in appetite and metabolism that could lead to weight gain, said study co-author Phyllis Zee, director of the Sleep and Circadian Rhythms Research Program at Feinberg.
The researchers compared 23 late sleepers – people who went to sleep around 3:45 a.m. and woke up by 10:45 a.m. -- with 28 “normal” sleepers, or those who were in bed by 12:30 a.m. and up by 8 a.m.
The late sleepers consumed extra calories during dinner and later in the evening when everyone else was asleep; they also had a higher body weight index, or weighed more, than normal sleepers. Overall the total calorie intake between the two groups was similar, but the behaviors of the late sleep group appeared to increase the risk of weight gain, said Zee.
“The difference may have to do with the availability of what’s around at night,” said co-author Kelly Glazer Baron, a health psychologist and neurology instructor at Northwestern’s Feinberg School of Medicine “If you’re in social situations, out with people or at restaurants, the food is different than what’s available at home.” Later sleepers also sleep about an hour less than those who turn in early.
Most research on sleep and obesity has looked at sleep quality and duration. This study looked at the relationship between the timing of sleeping and waking, dietary behavior and body mass index.
“There is evidence that sleep loss or shorter sleep duration affects metabolism by altering the ability of the body to handle glucose and also increases hunger hormones,” said Zee, medical director of the Sleep Disorders Center at Feinberg and Northwestern Memorial Hospital. “What this study shows is that timing may also alter when, how much and what type of food ones eats and metabolism.”
So will eating after 9 p.m. make you fat?
“It could increase your tendency to gain weight,” said Zee. “But we need more research to directly address this question.”Copyright © 2015, The Baltimore Sun