Those who work at night use fewer calories

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MunichNurses, doctors, bus drivers, bartenders, factory workers, police officers - they all have one thing in common: These professional groups sometimes have to work at night. It has long been known that this can affect your health. The reason is likely to be lower calorie consumption.

“If people who work at night don't adjust their eating habits, it can lead to obesity,” says Kenneth Wright. He and his colleagues from the sleep laboratory at Colorado University Hospital (USA) found that night workers use less energy overall than people who work during the day.

Six days of sleep laboratory

For their study, the scientists observed 14 healthy adults in the hospital for six days. In this way, the waking sleep rhythm of the test subjects, as well as their diet and hormonal balance, could be checked very precisely.

For two days the volunteers followed their normal rhythm: they worked during the day and slept at night. For the remainder of the trial, they had to work the night shift. The participants ate as much as they would normally eat at home and the duration of sleep was also the same as usual.

16 percent fewer calories

The result: only after the first night shift did the test subjects' energy consumption increase slightly: by an average of three percent. After that, however, the calorie burn gradually decreased by three percent per day, over the entire duration of the experiment by 12 to 16 percent.

“Humans have got used to being awake in daylight and then also to eat. The inner clock is therefore shaped by sunlight, ”says Wright. Apparently, daytime sleep disturbs the metabolism. Because at night the body rests and does not burn food as effectively. So if you work while others are sleeping, you should actually eat less. In the experiment, however, the subjects' levels of the hormones leptin and peptide-YY, which ensure a feeling of satiety, fell during the night shifts. This makes those affected feel less full. “Night shifts mean a fundamental intervention in the human body,” Wright sums up. (away)

Source: Wright K. P. et al .: Impact of circadian misalignment on energy metabolism during simulated nightshift work, Impact of circadian misalignment on energy metabolism during simulated nightshift work, PNAS, October 21, 2014.

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