How your body clock can lead to weight gain

It comes down to when your body releases melatonin, which marks the onset of sleep

Rachel Hosie
Wednesday 13 September 2017 09:01 BST
Eating too late or raiding the fridge on your way to bed could increase your risk of cancers
Eating too late or raiding the fridge on your way to bed could increase your risk of cancers (Getty/iStock)

Your body clock could be more responsible for weight gain than you thought, a new study has found.

Different people have different approaches to timing your meals if you want to lose weight or stay healthy.

Some argue you shouldn’t eat less than two hours before bed, and others advocate waiting until lunchtime to eat your first meal of the day, thus giving your body a fasting period overnight.

But little research has been conducted into how our eating habits can be affected by our sleeping patterns - until now.

The study by the Brigham and Women’s Hospital in Boston, Massachusetts, US, has discovered how mealtimes affect your weight gain, based on what time you wake up and go to sleep.

They analysed data from 110 adults aged 18 to 22 to document sleep and circadian behaviours within their regular daily routines.

Using an app, all their food intake was logged for seven consecutive days during their regular daily routines. Body composition and timing of melatonin release (which marks the onset of sleep) was assessed in a laboratory.

The researchers found that the most important thing is to wait a few hours after eating before going to bed, so your body has time to digest.

The participants with the highest body fat percentages consumed most of their calories shortly before bed, when their levels of melatonin were high.

In contrast, those with lower percentages of body fat tended to go to bed a few hours after finishing eating.

Our metabolism is affected by our circadian rhythm, and this varies greatly from person to person, whether due to irregular work shifts or simply natural preference for rising early or staying up late.

“We found that the timing of food intake relative to melatonin onset, a marker of a person’s biological night, is associated with higher percent body fat and BMI, and not associated with the time of day, amount or composition of food intake,” lead author Andrew McHill, Ph.D., researcher with the Division of Sleep and Circadian Disorders at BWH, said.

“These findings suggest that the timing of when you consume calories, relative to your own biological timing may be more important for health than the actual time of day,” he added.

The researchers accepted that university-aged students may not be representative of the population as a whole, but they concluded that the study’s results provide evidence that the consumption of food during the circadian evening plays an important role in body composition.

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