A new study has found a link between working night shifts and being overweight.
Researchers from the Chinese University in Hong Kong studied shift patterns and how they impacted health, and found a nocturnal schedule can affect the metabolism.
The chance of becoming obese increased by 29 percent - nearly a third - for those working at night.
The analysis, published in Obesity Reviews, found exposure to artificial light affects the body clock, in turn affecting the release of hormones. Night workers burned up to 16 percent fewer calories.
The study also found a heightened risk of abdominal obesity, where fat builds around the stomach.
"Globally, nearly 0.7 billion workers are engaged in a shift-work pattern," senior study author Dr Lap Ah Tse says.
"Our study revealed much of the obesity and overweight among shift workers is attributable to such a job nature."
Nursing, security, policing and transport are all jobs with a high likelihood of night shifts.