Longer working hours are linked to higher obesity rates, prompting fresh calls for a four-day week.
International research presented at the European Congress on Obesity in Istanbul compared working patterns and obesity prevalence across 33 OECD countries from 1990 to 2022.
The study found that countries such as the US, Mexico and Colombia, which have longer annual working hours, also had higher obesity rates, even though northern European countries consume more energy and fat on average than those in Latin America.
Reducing annual working hours by 1 per cent was associated with a 0.16 per cent decrease in obesity rates.
The authors concluded that lack of time for exercise and work-related stress could explain the link.
Dr Pradeepa Korale-Gedara, lead author of the study at the University of Queensland in Australia, said increased stress raised levels of cortisol, a hormone released during stress, causing people to store more fat, while some jobs also left people unable to burn energy.
“When people have a more balanced life, they have a better life,” the researcher said.
“They have less stress, they can focus on more nutritious food and engage in more physical activities.”
Although researchers warned the study does not prove causation and that income levels in different countries could also be a factor, it has prompted experts to renew calls for a four-day week in the UK.
About 200 companies have already adopted the working pattern for employees.
South Cambridgeshire district council, whose Liberal Democrat administration won 43 out of 45 seats in the local elections last week, has also introduced a four-day week for all staff.
Office for National Statistics data shows more than 200,000 workers have switched to a four-day week since the Covid-19 pandemic.
James Reeves, a campaign manager at the 4 Day Week Foundation, said: “A four-day week on full pay could slash Britain’s obesity levels by giving millions the time they need to ditch bad habits and make healthier choices.
“It’s essential that local and national governments seriously consider the role that a shorter working week can play in improving the health of our communities.
“The nine-to-five, five-day working week is 100 years old and we’re long overdue an update.”
Dr Rita Fontinha, a psychologist at the University of Reading, who published a review of evidence on the four-day week last year and has been funded by the Portuguese government to pilot a four-day working week there, said obesity was closely related to time poverty.
“If you work two jobs or long hours, you simply do not have the energy to cook and it becomes easier to just buy something packaged or processed.
“A four-day week or different forms of working-time reduction could be associated with better choices in terms of food, exercise and sleep to contribute to healthier societies.”
But ministers remain opposed to four-day weeks.
A government spokesperson said: “This government will not mandate a four-day work week for five days’ pay.
“But through the Employment Rights Act, we’re making it easier for flexible working requests to be accepted.”