Eating late at night can lead to weight gain: Study

To test whether the timing of meals could influence body weight, a research team from the Center for Sleep and Circadian Biology at Northwestern University, Illinois, carried out research in mice and found that late-night snacking could make a big difference.

The team found that eating at odd times, such as in the middle of the night when most people are sleeping, add extra pounds to your weight.

Study details
To reach their findings, Fred Turek, professor of neurobiology and physiology in the Weinberg College of Arts and Sciences and director of the Center for Sleep and Circadian Biology, and colleagues studied two groups of mice.

All the mice were fed the same high-fat diet, and all performed the same amount of exercise. The only difference was that one group was fed the diet during the daylight hours when they would normally be awake, while the other group was given the same food during normal sleeping hours.

"One of our research interests is shift workers, who tend to be overweight," said senior author of the study Deanna M. Arble, a doctoral student in Turek's lab. "Their schedules force them to eat at times that conflict with their natural body rhythms.

“This was one piece of evidence that got us thinking -- eating at the wrong time of day might be contributing to weight gain. So we started our investigation with this experiment."

After six weeks of follow-up, Turek’s team found that mice that ate a high-fat diet during normal sleeping hours increased their body-weight by 48 percent than mice eating the same type and amount of food during naturally wakeful hours. Mice in the latter group posted an average increase of 20 percent of the body weight.

Circadian clock governs daily cycles of feeding
Eating meals late or at irregular times could affect body weight, and it’s all because it disrupts the body's circadian rhythms, the body's internal clock, scientists claim.

The body’s natural rhythms have a role in how our bodies use up energy, the research suggests.

"How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out," said Turek. "We think some factors are under circadian control.”

The researchers believe their findings could significantly help health experts develop strategies to combat human obesity, a known risk factor for cardiovascular complications, diabetes, high blood pressure, and a host of other health conditions. More than 300 million adults around the world are obese, including more than a third of American adults.

“Better timing of meals, which would require a change in behavior, could be a critical element in slowing the ever-increasing incidence of obesity," added Turek.

The findings were published online Sept. 3, 2009 in the journal Obesity.