Why eating at night will make you gain weight

Source: Web exclusive: September 2009

It’s one of the most pervasive questions in weight-loss theory: does when you eat affect how many pounds you gain or lose? It turns out the answer is yes’but primarily for mental, rather than physical, reasons.

Weight gain that is attributed to snacking at night is generally thought to be caused by the overeating that’s done at late hours, rather than the actual time of day. “Some people who wake up in the middle of the night to eat [can] gain weight because they are usually eating for emotional reasons,” says Jessica Begg, a registered dietitian based in Vancouver.

Dr. Arya Sharma, chair for Cardiovascular Obesity Research and Management at the University of Alberta, adds that people who save eating for late hours also tend to make poor food choices.

“One of the problems with eating at night is that people are not eating enough during the day,” says Sharma. If you’re tired and famished by the time evening comes around, you’re more likely to eat whatever is convenient (such as junk food) and consume most of your day’s calories at a time when your metabolism is slowing down due to lack of food during the daytime.

However, Sharma says that weight gain from night eating may go beyond the types of foods we choose at that time. He points to a study by a team of researchers from Northwestern University in Illinois that fed two groups of mice the same amount of calories at different times of the day. One group was fed at night, which is when nocturnal mice usually eat, and the second group was fed during the day when mice usually sleep. “The mice that were given the calories when they should have been asleep gained so much more weight than the ones that were fed at night [when mice are usually awake],” he says.

More research has yet to be done to connect these findings to humans, but Sharma says you might want to consider that nighttime calories may cause weight gain.

And if you do feel peckish at night, make sure your bedtime nibble is small and controlled. Begg suggests choosing a snack that includes two of the food groups, such as nuts and a piece of fruit, cheese and crackers or even a glass of milk and a cookie.

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