Research finds employees who sleep during day burn fewer calories than when sleeping at night

This article is more than 5 years old

This article is more than 5 years old

Sleeping during the day burns fewer calories than at night, according to research that shows working night shifts can increase the risk of developing obesity.

A new study has found that night shift patterns disrupt the metabolism of employees, causing them to use less energy than they normally would over the course of a day.

The effect was particularly pronounced when the employees were trying sleep during the day as, despite suffering more disturbed sleep, they burned between 12% and 16% fewer calories than when sleeping at night.

The findings may help to explain why those who work night shifts are more likely to suffer from obesity and related diseases such as heart disease.

Dr Kenneth Wright, director of the sleep and chronobiology laboratory at the University of Colorado, said lower energy use may accentuate the poor diet and lack of exercise that is often seen in night shift workers. He said this may be due to a mismatch between the body’s internal circadian clock and sleep patterns that disrupts normal metabolism.

He said: “Specifically, the 52-59kcal lower total daily energy expenditure on night shifts, if recurrent without a reduction in food intake, would contribute to weight gain.

“As little as 50 kcal excess calorie storage per day can increase weight over time and if increased exhaustion and fatigue levels associated with shift work results in reduced physical activity levels, this would promote weight gain.”

An estimated 4.1 million people work shifts and with the increasingly global nature of business working through the night to match other timezones is becoming more commonplace.

Shift work has been associated with a range of health problems including an increased risk of diabetes, heart disease and stroke. But scientists have struggled to explain why eating at different times of the day and changing sleep patterns can lead to weight gain.

Previous research has shown that people working night shifts tend to have poorer diets, with the food available to them during the night tending to be less healthy.

In the latest study, which is published in the journal Proceedings of the National Academy of Sciences, 14 healthy adults were put through a simulated night shift and day shift pattern in a laboratory over a six-day period. The scientists analysed the volunteers’ energy use, nutrient use and hormone levels alongside their sleep patterns.

They found that energy use increased by 4% on the first night shift, then fell by around 3% on each of the two following days when compared to day shift patterns. The participants also used less carbohydrate and protein during the night shift pattern.

Wright said more work needed to be carried out to see how rotating shift patterns and additional night shifts may further affect the metabolism.