The next time you have a hankering for a bag of chips or a chocolate chip cookie, look at the clock. A new study published in the journal Current Biology found the body expends 10% more calories at rest during the late afternoon and early evening compared to the early morning. Thus, indulging in a sweet treat during that window could make it easier to burn off the calories instead of storing them as fat.
THE SCIENCE
The research theorizes that the body’s circadian rhythm could be the reason for different calorie burns at different times of the day. The 24-hour internal clock not only governs your sleep/wake cycle, but also regulates hormones that control hunger and appetite.
The Current Biology findings support the idea that eating at 5 a.m., when your body burns the fewest calories at rest, could make it harder to control your weight than eating 12 hours later when your body is primed to burn the most calories. Additional research found calorie burn began dropping in the evening (as the sun went down) and remained low throughout the night.
“It looks like energy expenditure follows a circadian rhythm, which makes sense, since humans evolved to eat and be active during the day and then fasted while sleeping overnight,” notes study co-author Josiane Broussard, PhD, an assistant professor at Colorado State University. “If you eat later at night when your energy expenditure is lower, you are more likely to store excess calories rather than burn them.”
HOW MEAL TIMING AFFECTS WEIGHT MANAGEMENT
While connections between circadian rhythm and calorie burn are still being studied, there is robust evidence that meal timing affects weight management. One study found overweight and obese women who consumed 700 calories at breakfast, 500 calories at lunch and 200 calories at dinner experienced greater weight loss and higher reductions in waist circumference than those who consumed their calories in reverse (200 calories at breakfast, 500 calories at lunch and 700 calories at dinner).
Eating late-night meals or snacks could also interfere with the release of insulin, making it harder for your body to use the sugar in food, according to a separate 2019 study.
“Your body needs fuel from the moment you get up until the moment you get home,” says Joan Salge Blake, RD, professor of nutrition at Boston University. “If you eat the majority of your calories in the evening while you sit on the couch watching TV and your body is burning fewer calories, it’s going to make it harder to manage your weight.”
THE BOTTOM LINE
Factors like shift work and international travel may make it necessary to eat at odd times, but try to maintain a “normal” meal schedule and eat more energy-dense foods earlier in the day, when your body has the greatest chance to burn more calories, suggests Broussard. This strategy, along with a well-balanced diet and regular movement, can help keep the number on the scale from creeping up.
