How Many Calories Do You Burn While Resting?

When it comes to burning calories, the latest research suggests that timing is everything. The claim comes from a recent report published in Current Biology and affirms that the number of calories burnt during periods of rest is directly linked to the time of day.

This is because the body's resting metabolism is heavily dependent on circadian rhythms, i.e. the biological process that governs the body according to a 24-hour cycle. As well as influencing the sleep-wake cycle, circadian rhythms also impact other important bodily functions like digestion and metabolism.

The all-important circadian rhythm

The study was fronted by Jeanne Duffy, a neuroscientist at the Brigham and Women’s Hospital in Boston. After exploring the link between circadian rhythms and metabolism, Duffy and her team found that during periods of rest the body burns 129 more calories in the afternoon and evening, as opposed to early in the morning. Evenings also switch the body into top gear when it comes to burning fat. While mornings may not be primetime for burning calories, the researchers noted that carbohydrates are burnt at a higher rate during the AM hours.

The findings add to a building body of research suggesting that eating and sleeping patterns could play an important role in maintaining good health. This is largely because core bodily functions like breathing, blood circulation and brain activity all rely on calories.

Afternoons pinpointed as peak calorie burning timeslot

The unconventional study tracked the physical health of seven patients who were housed in windowless rooms for three weeks. None were given access to a clock and all were sent to bed four hours later than the previous night, a strategy designed to throw off the circadian rhythm and mimic the impact of flying around the world and crossing all time zones in just one week.

Duffy and her colleagues observed that all participants adhered to clear rhythms when burning calories, with highs and lows varying from person to person. For example, resting calorie burning rates peaked at around 5pm on average, while the least efficient time was around 5am.

Duffy asserts that these sorts of variations are normal and can help explain while some people are early birds and other are night owls. Regardless, she stresses that the timing of daily rhythms can have a significant impact on metabolism rates, as well as overall health.  

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