Longer working hours are linked to higher obesity rates, a study presented at the European Congress on Obesity (ECO 2026) in Istanbul has found.
The international research, led by Dr Pradeepa Korale-Gedara of the University of Queensland, Australia, compared working patterns and obesity prevalence across 33 OECD countries from 1990 to 2022. It identified a clear association: nations with longer annual working hours, such as the United States, Mexico and Colombia, also recorded higher obesity rates. Conversely, a reduction of just one per cent in annual working hours was associated with a 0.16 per cent decrease in obesity prevalence across the whole population.
Stress, cortisol and the squeeze on time
The study points to several mechanisms linking extended working hours to weight gain, with stress and reduced physical activity receiving the most detailed explanation. Researchers said that long hours spent at a desk leave less time for exercise. But beyond simple time constraints, the pressures of a demanding work schedule can trigger stress-related eating and elevate cortisol levels, both of which are known to promote fat storage and weight gain.
“When people have a more balanced life, they have a better life,” Dr Korale-Gedara said. “They have less stress, they can focus on more nutritious food and engage in more physical activities.”
Data analysed for the period 2000–2022 showed that a one per cent reduction in working hours was associated with a 0.13 per cent fall in obesity rates, with the effect being more pronounced in the earlier years of the study (1990–2010) than in more recent decades. The impact also varied by gender: among men, a one per cent reduction in hours was linked to a 0.23 per cent decrease in obesity, while for women the figure was 0.11 per cent. The study did not prove causation, and researchers stressed that other socio-economic and cultural factors are at play.
Country-specific data and the UK picture
As of 2022, the United States had the highest adult obesity rate among OECD countries at 41.99 per cent, while Japan recorded the lowest at 5.54 per cent. Several others – including Chile, Mexico and New Zealand – reported rates above 30 per cent. In contrast, many Northern and Western European nations kept obesity below 20 per cent. The United Kingdom sat between these extremes at 26.8 per cent, though it still ranks among the worst in Europe. Around 3.8 million children aged five to 19 in the UK have a high body mass index – roughly twice the number of overweight or obese children in France and Italy.
Working hours data for 2022 show that the UK averaged 1,505 hours per year per worker – markedly higher than the lowest-hour countries such as Germany (1,340), Norway and Belgium (both 1,422), and Sweden (1,436). At the other end of the scale, Colombia averaged 2,282 hours, Mexico 2,226, and the United States 1,811.
The findings have prompted renewed calls for a four-day working week in the UK, where more than 200 companies have already adopted the model, and South Cambridgeshire district council has implemented it for all staff. The government has said it is not in favour of mandating a shorter week.
Beyond working hours: the complexity of obesity
The researchers considered a range of additional factors that help explain national differences in obesity. Higher income levels, measured by GDP per capita, were linked to lower obesity rates: a one per cent increase in GDP was associated with a 0.112 per cent reduction in obesity (0.16 per cent for men and 0.11 per cent for women). However, the relationship is not straightforward – a 2004 study noted that a $1,000 increase in per capita GDP was associated with a 0.172 percentage point rise in obesity, suggesting that economic development can initially drive weight gain before other influences take hold.
Urbanisation appeared protective, with a one per cent increase linked to a 0.02 per cent drop in obesity. Researchers said supportive urban environments – including access to healthy food and exercise facilities – may play a role. Higher food prices were also negatively associated with obesity, implying that cost can steer dietary choices.
Surprisingly, preliminary analysis showed that average national energy and fat intake were not strongly correlated with obesity rates. For instance, Latin American OECD countries had lower energy and fat intake than several European nations yet recorded higher obesity, challenging the assumption that rising calorie consumption is the sole driver.
Other socio-economic gradients remain central. In Germany in 2003, women in the lowest income group were three times as likely to be obese as those in the highest. Lower educational attainment, particularly among women, has also been linked to higher obesity. Shift work, with its disruption of sleep patterns and reduced access to healthier food, is another recognised contributor. Further studies on OECD countries have identified sugar consumption, low birth weight and alcohol intake as positively associated with obesity, while protein intake and smoking were negatively associated.
Previous research adds nuance. A meta-analysis of 19 cohort studies involving 122,078 people found that working 55 hours or more per week increased the risk of moving from normal weight to overweight, but not from overweight to obesity. Another study indicated that working more than nine hours a day was associated with being overweight or obese in women over 50. Some research suggests that while long hours may contribute to becoming overweight, they do not necessarily lead to weight loss among those already obese.
Globally, adult obesity has more than doubled since 1990, and adolescent obesity has quadrupled. Across OECD countries, the proportion of the population with obesity rose from 13 per cent in 2003 to 19 per cent in 2023. Researchers point to the consolidation of “obesogenic environments” over the past 20 to 30 years – physical, social and economic settings that favour calorie-dense diets and sedentary lifestyles. In low- and middle-income countries, a shift away from traditional diets toward Western-style eating high in sugar and fat is creating a double burden of under- and over-nutrition.
Dr Korale-Gedara and her colleagues concluded: “The findings suggest that the relationship between working hours and obesity is complex and influenced by various socio-economic and cultural factors. These patterns point to potential mechanisms such as reduced time for physical activity, increased work-related stress, and greater reliance on energy-dense convenience foods.” Higher GDP, urbanisation and food prices “may facilitate healthier dietary choices”, they added, but the interplay of income, culture and workplace demands means there is no single lever to pull.
