Those who work longer hours are more likely to be obese and cutting how much time you spend working could help you keep the weight off, research suggests.

International research presented at the European Congress on Obesity in Istanbul compared working patterns and obesity prevalence for 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% was associated with a 0.16% decrease in obesity rates. The authors concluded that lack of time for exercise and work-related stress could explain why those who clock off last are more likely to pile the weight on. Dr Pradeepa Korale-Gedara of the University of Queensland, Australia, the lead author of the study, said increased stress raised levels of the hormone cortisol, causing people to store more fat, while working in jobs where they were unable to burn energy.

“When people have a more balanced life, they have a better life,” she said. “They have less stress, they can focus on more nutritious food and engage in more physical activities.”

Although researchers warn the study does not prove causation and income levels of 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 adopted the working pattern for their employees already. And South Cambridgeshire district council, whose Liberal Democrat administration won 43 out of 45 seats in the local elections last week, has 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.”