November 08, 2018
Burning calories is a major perk of working out — especially if you are trying to lose weight or gain muscle.
But, as you know, the human body doesn’t only burn calories while sweating — we burn calories all the time! Still, certain times of the day are best for peak calorie burning, a new study finds.
Circadian rhythms, which control the body’s internal clock and sleep and wake cycles, are likely the reason that your body burns calories at different speeds throughout the day, according to a small study published in Current Biology.
At rest — the times when you aren’t working out or moving, really — humans burn about 10 percent more calories in the late afternoon than they do late at night, the study found. This is probably a big reason why nutritionists warn against late-night snacking.
According to study co-author Dr. Jeanne Duffy, an associate professor of medicine at Harvard Medical School and a neuroscientist at Brigham and Women’s Hospital, that 10 percent adds up to be an additional 130-or so calories burned in the late afternoon, without you doing anything differently, TIME reports.
The study, which we mentioned was small — examining only seven people — men and women, ages 38 to 69 for 37 days straight in a lab without clocks, windows, phones or Internet, as to remove any sort of disruption. Researchers also regulated everything from people’s diets to their light exposure, as to really hone in on the natural impact of circadian rhythms.
Each of the seven participants wore sensors that measured their core body temperatures, allowing researchers to measure energy expenditure: the higher the core temperature, the more calories the person was burning. Researchers found that body temperature was lowest when circadian rhythms corresponded with late night and early morning, and at their highest about 12 hours later, in the late afternoon. Researchers confirmed this by shifting participants' wake-up and bed times by four hours each day.
At this point, you’re probably thinking: “Sweet, I’ll start working out in the late afternoon so I can burn the most calories as possible!” But the researchers can’t say, based off this small study, whether people should reschedule their workouts and meals around this late-afternoon energy surge. Rather, if you take anything from this study, researchers suggest avoiding the body’s calorie-burning dip in the late night and early morning.
So, maybe a big ol’ cowboy breakfast of steak, eggs and potatoes, isn’t the best way to start your day after all.