Researchers have found that sleeping during the day uses fewer calories than sleeping at night, which implies that working night shifts increases the risk of becoming obese.
The study has found that night shift patterns are responsible for the disruption of workers’ metabolism. It causes them to use less energy than they would normally do over the course of the day. This effect was more pronounced when the workers tried to sleep during the day as they not only suffered more disturbed sleep, but they also burned between 12% and 16% fewer calories than if they were sleeping at night.
These results may aid in the explanation as to why people working night shifts are more likely to suffer from obesity and its complications, such as heart disease.
The director of the sleep and chronobiology laboratory at Colorado University, Dr Kenneth Wright, said the use of lower energy amounts may be accentuated by the lack of exercise and poor diet that is often present in night shift workers. He said this could be due to a disparity between the internal circadian clocks of the body and sleep patterns which disturb normal metabolism.
He added that the 52 to 59kcal lower total daily expenditure of energy when working night shifts, and not reducing food consumption, would lead to weight gain. He added that as little as 50kcal of excess calorie storage on a daily basis will increase weight over time and if there is increased tiredness and fatigue levels linked to shift work, it will result in a reduction of physical activity levels, which would compound the weight gain.
Around 4.1 million people work shifts and this is increasing because of the global nature of business and the attempt to matching differing time zones.
Shift work has already been linked to a range of health issues, including stroke, heart disease and diabetes. However, scientists have been unable to explain why eating at different times of day and the change in sleep patterns could result in weight gain.
Previous research indicated that those working night shifts generally have poor diets as the food available to them during the night is normally less healthy.
The latest study involved putting 14 healthy adults through a simulated day and night shift pattern. The simulation took place in a laboratory over a period of six days. The participants’ energy use, hormone levels and nutrient use, as well as their sleep patterns were analysed by the scientists.
They discovered that the use of energy increased by 4% during their first night shift, then it started falling by about 3% on the following two consecutive days, when compared to day shift patterns. It was also found that the participants used fewer carbohydrates and protein when they were on the night shift pattern.
Dr Wright said it was necessary to do more research to determine the effect of additional night shifts and rotating shifts on metabolism.
Image Credit: Sandra Cohen-Rose and Colin Rose