People who work night shifts have a 35 percent higher risk of obesity because the nocturnal schedule derails their metabolism, a study claims.

Artificial light during night shifts disrupts the brain's melatonin levels and hinders the body's metabolism.

Someone who works at night will then gain more weight quicker because the metabolism is working slower than normal.

More than 3.4 million people worldwide die every year from obesity related ailments including diabetes, stroke and cardiovascular disease.

Experts recommend altering the work schedule to avoid working night hours in order to reduce the global obesity epidemic.

People who work night shifts increase their risk of developing obesity by one third. Researchers studied the shift patterns of hundreds of thousands of people. They found that night shifts derailed the metabolism causing people to gain weight (file photo)

Researchers from the Chinese University in Hong Kong analyzed the shift patterns of employees and how it compared to their health.

His team pooled data from 28 previous studies involving hundreds of thousands of participants across the world including healthcare workers, manufacturing employees, local government staff and bus and truck drivers.

Senior author Dr Lap Ah Tse said: 'Globally, nearly 0.7 billion workers are engaged in a shift work pattern.

'Our study revealed much of the obesity and overweight among shift workers is attributable to such a job nature.'

They found night shift workers had a 29 percent increased risk of becoming obese or overweight.

'Obesity has been evident to be positively associated with several adverse health outcomes, such as breast cancer and cardiovascular diseases,' Dr Tse said.

The analysis, published in Obesity Reviews, also showed the risk of abdominal obesity, the most dangerous type where fat builds around the stomach and damages organs, was 35 percent greater.

Dr Tse said exposure to artificial light at night disrupts the body clock, or circadian rhythm, reducing production of the sleep hormone melatonin that plays an important role in preventing disease.

Obesity has been evident to be positively associated with several adverse health outcomes, such as breast cancer and cardiovascular diseases Dr Lap Ah Tse, senior author from the Chinese University in Hong Kong

Melatonin regulates the sleep cycle and also hormones such as cortisol, insulin and leptin but disrupting it may harm metabolism, leading to night workers gain weight.

Throughout the world, around 3.4 million deaths a year are caused by obesity related diseases.

These diseases include diabetes, heart disease, stroke and forms of cancer.

Shift work is becoming popular among employees because of the high demand for flexibility and productivity in the current work environment.

But evidence has identified a link with obesity that can trigger the development of several cancers, such as breast cancer, as well as cardiovascular diseases.

Previous research has shown sleeping during the day burns fewer calories than at night.

Despite suffering more disturbed sleep, night shift workers burned between 12 and 16 percent fewer calories.

'Modification of working schedules to avoid prolonged exposure to long-term night shift work might be an efficient administrative control to reduce the risk of obesity,' Dr Tse said.