A continuing rise in obesity around the world is not inevitable, research suggests, with rates in some countries levelling off or potentially in decline.

Researchers say focusing on what has been described as a global epidemic of obesity hides large variations in trends across different countries, sexes and age groups.

Majid Ezzati, a professor of global environmental health at Imperial College London and author of the study, said: “I think the thing that’s really important is this diversity exists even across countries that have really similar economic, environmental, technological features. So countries may look the same on the surface of it but obesity looks different.”

Writing in the journal Nature, the international team, which involved a network of almost 2,000 researchers, described how for each country they calculated the change in the prevalence of obesity each year between 1980 and 2024. They drew on data from 4,050 population-based studies involving 232 million participants aged five years and above.

They found that the prevalence of obesity increased in almost all countries over the 45-year period. However, in most high-income countries, a rapid rise in the prevalence of obesity has been replaced by a slower increase, a plateau, or a potential decline.

The rate of growth in obesity is slowing in adults in the US and UK, reaching a prevalence of 40-43% and 27-30% respectively in 2024. Obesity is increasing steadily in Finland, has plateaued in Germany and may have started to decline in France, where 24-25%, 20-23% and 11-12% of adults respectively were thought to have the condition in 2024.

Slowdowns were often seen in children and adolescents before adults. For the former group, the slowdown started as early as 1990 in Denmark and rates stabilised in most high-income countries by the mid-2000s. Obesity has plateaued in boys and girls in the UK, US, Germany and Japan at prevalences of 10-12%, 20-23%, 7-12% and 3-7% respectively.

Meanwhile, obesity among young people and adults in many low-income and middle-income countries continues to rise and in some cases this is accelerating.

The team say it is important now to unpick what is behind the trends in different countries. The situation is complex: while there may be shared reasons for obesity, such easy access to unhealthy foods or a decrease in physical activity, the team say country-specific factors rooted in social, economic and policy considerations could also be important, from perceptions around body image to the presence or absence of interventions such as healthy school meals.

Naveed Sattar, a professor of metabolic medicine at the University of Glasgow, who was not involved in the work, said the study highlighted how obesity trends were diverging sharply across countries. “English‑speaking nations are doing particularly poorly, with the UK now among the countries with the highest obesity levels worldwide,” he said.

Sattar said it was encouraging that some countries appeared to have reached a plateau in obesity rates. “Understanding what has worked in those settings is crucial as it could help shape more effective public health strategies for the UK,” he said, although he noted there could be country-specific aspects or customs at play.

He said the rapid rise in obesity across many developing countries was especially concerning, not least as it could result in increases in diabetes and cardiovascular conditions.

He added: “Looking ahead, it will be important to see how wider use of effective weight‑loss medicines affects obesity trends, particularly in the UK and the United States. Recent signs of stabilisation in the USA suggest there may be room for cautious optimism. Combining evidence‑based medicines with strong public health measures could begin to shift obesity rates in the right direction.”