homehome Home chatchat Notifications


You burn more calories in the afternoon than in the morning

A story about metabolism, circadian rhythms, and calories.

Alexandra Gerea
November 8, 2018 @ 7:02 pm

share Share

All other things equal, you consume about 10% more calories in the afternoon than in the morning — something which surprised even researchers.

“The fact that doing the same thing at one time of day burned so many more calories than doing the same thing at a different time of day surprised us,” says Kirsi-Marja Zitting of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital and Harvard Medical School, lead author of the paper.

A calorie is essentially a measure of energy. Our bodies get energy from food, and that energy can be measured in calories. Although it’s technically unofficial, the calorie is by far the most common measure of food energy, and is a common talking point of most diets and nutritional strategies.

If you’ve ever kept an eye on your calorie intake and consumption, then you probably know what the Resting Metabolic Rate is — essentially, it’s a measure of how many calories the body consumes without doing anything. Think of it this way: you get energy from food, and you burn some of it just by existing; it’s pretty nice.

Zitting and colleagues wanted to see how calorie consumption is affected by the time of day, so they studied seven people in a special laboratory without any clues about what time it was outside. There were no clocks, windows, phones, or Internet. Participants were given fixed hours when they had to go to bed and, to make things even more confusing, those times were adjusted four hours later each night.

“Because they were doing the equivalent of circling the globe every week, their body’s internal clock could not keep up, and so it oscillated at its own pace,” co-author Jeanne Duffy, also in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital, explains. “This allowed us to measure metabolic rate at all different biological times of day.”

They found that the circadian rhythm has a strong impact on the resting metabolic rate. During the biological night, when the body cools down slightly, calorie consumption was lowest — which makes a lot of sense. What was unusual, however, was that energy consumption was highest 12 hours later, during the biological afternoon — 10% more than the normal rate. The participants’ respiratory quotient, which reflects macronutrient utilization, also varies by circadian phase, and the two may be connected.

This adds to an already growing number of studies showing that our metabolic rates differ greatly — not only from person to person, but also from time to time.

“It is not only what we eat, but when we eat–and rest–that impacts how much energy we burn or store as fat,” Duffy says. “Regularity of habits such as eating and sleeping is very important to overall health.”

Next, the team will look at how appetite and the body’s response to food vary with time of day.

Journal Reference: Current Biology, Zitting et al.: “Human Resting Energy Expenditure Varies with Circadian Phase” https://www.cell.com/current-biology/fulltext/S0960-9822(18)31334-4

share Share

Drones Helps Researchers Uncover a Lost Mega-Fortress in Georgia

Researchers have long known about the formidable scale of the Dmanisis Gora fortress, but a recent study has unveiled its true magnitude. Using drone-based imagery and photogrammetry, a team of scientists has revealed that this 3,000-year-old structure in the Caucasus Mountains spans an astonishing 60 to 80 hectares. A cultural crossroads The South Caucasus is […]

James Webb Telescope Uses Cosmic "Magnifying glass" to Detect Stars 6.5 Billion Light-Years Away

The research group observed a galaxy nearly 6.5 billion light-years from Earth; when the universe was half its current age.

Eating more peanuts, herbs, and spices can boost your gut microbiome

A small change in diets can make a big difference for your health.

Did your rent just surge? Blame this price-fixing AI landlord costing Americans $3.6 billion annually

AI is changing the housing market and renters are paying the price.

Melting Antarctic Ice Could Awaken 100 Hidden Volcanoes

As ice recedes, hidden volcanoes under Antarctica awaken, reshaping predictions for climate change.

This Hornet Can Drink 80% Alcohol Without Ever Getting Drunk and Scientists Finally Know Why

Oriental hornets never get intoxicated with alcohol no matter how strong the alcohol or how long they drink.

200 Jurassic-era dinosaur footprints unearthed on UK’s largest dinosaur highway

Thanks to a storm, these dinosaur footprints managed to remain preserved for 166 million years.

The Soviets sent most of its intellectuals to remote gulags. Decades later, those areas became more prosperous

A new study reveals that regions near Soviet GULAG camps are more prosperous today, thanks to the unintended legacy of intellectual capital of educated prisoners

Strange Painted Penis Bone Found in England Reveals Rituals From Roman Britain

An enigmatic artifact suggests ancient rituals tied to fertility and agricultural cycles.

Not armed, but dangerous: New Armless dinosaur species unearthed in Argentina

This dino was not armed, but still very dangerous!