Please don’t call this an “obesity pandemic.” That one-size-fits-all label no longer captures the diverse trajectories of weight gain around the world, a new report claims. Obesity rates are slowing or even trending downward in some countries, and the trend is highly correlated with a country’s wealth.
Instead, looking at speed to see how far obesity is increasing, or not, reveals that rates continue to rise in most low- and middle-income countries, have plateaued in most high-income countries, and may be declining in some wealthier regions.
“An increase is inevitable,” Majid Ezzati, professor of public health at Imperial College London and academic director of healthcare coalition Imperial Global Ghana, said at a media briefing on Tuesday. The leader of the new study also acknowledged that progress has yet to be made in most parts of the world.
“In most low- and middle-income countries, prices are rising steadily or accelerating,” he said. “Some of these levels exceed those of high-income countries.”
Viewing obesity through this lens elicited a variety of reactions.
William Dietz, a professor of exercise and nutrition science at the George Washington University School of Public Health, told STAT that he is perplexed by the “bizarre approach” of looking at trajectories based on year-to-year changes in body mass index (BMI) and obesity prevalence, which is difficult to interpret.
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“If one conclusion is that obesity has increased significantly in many places and continues to increase in most places, that’s not news,” David Allison, chief of nutrition in the division of pediatrics at Baylor College of Medicine, told STAT.
The study authors said their approach highlights useful points for comparison, for example by spotlighting outliers like the United States.
Obesity rates among children and adolescents have plateaued in the United States, the paper said, but obesity rates among adults are still rising, although not as high as they used to be. While this may be an encouraging trend, the United States still has the highest obesity rate in the world and first among high-income Western countries. Obesity rates among Americans range from 20% to 23% for girls and boys and 40% to 43% for women and men. In Japan, the rates are in the single digits overall: 3% to 7% for girls and boys, and 4% to 8% for women and men.
Globally, obesity was advancing faster in 2024 among women in 84 of 200 countries and men in 109 of 200 countries than in any other year in 45 years, the authors said in a paper published Wednesday in the journal Nature.
“We have diverse trajectories across countries,” Ezzati said. “This diversity actually exists even in countries with similar economic, environmental and technological characteristics. What’s surprising to me is how much effort we have to go to dig into what underlies some of these differences.”
The analysis tracked obesity prevalence, as measured by BMI, from 1980 to 2024. The authors are part of the NCD Risk Factor Collaboration, an international group of 2,000 scientists who study non-communicable diseases. They utilized a database of heights and weights of 232 million participants in more than 4,000 population-based studies around the world.
They found that the increase in obesity rates has leveled off in most high-income countries. Interest rates appear to be falling in France, Italy and Portugal, but it is too early to tell whether this is a permanent change.
It’s also too early to know what effect obesity drugs will have, the study authors said.
“The uptake of these obesity drugs is increasing, so this trend may be influenced in the future. But I think what’s really important is that we don’t lose sight of the importance of prevention,” co-author Jennifer Baker, president-elect of the European Obesity Society, said at a press conference. “Maybe if we go back five to 10 years from now, we’ll see something completely different.”
The reasons for the different prices vary by country. Although the Nature paper does not aim to establish cause and effect, Ezzati alluded to research from others on factors that may explain why obesity rates are rising in some regions and easing in others.
After World War II, the advent of industrial and commercial foods allowed people to eat fruits and vegetables all year round. It also became easier to eat both good and bad food. Knowledge about obesity has since helped people make healthy food choices, making it possible for obesity rates to moderate or even stall, especially when institutions support healthy choices.
Study co-author R. Guha Pradeepa of the University of Madras said at a press conference that India and other Asian countries are not experiencing a plateau, but rather obesity is accelerating.
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She pointed out that economic growth and rapid urbanization have limited space for walking, biking and playing. Then there’s the food.
“In low socio-economic countries, we are seeing a rapid shift away from traditional foods, diets rich in whole grains, vegetables and legumes, to energy-dense processed foods high in refined grains, sugar, salt and saturated fat,” she said in a briefing.
Carolyn Bramante, an assistant professor at the University of Minnesota Medical School who cares and researches obesity in adults and children, said there is a growing appreciation for two exposures she sees in children in her practice: sleep and screen time.
“Screen use disrupts sleep and also eliminates much of the non-exercise active heat production that occurs throughout the day,” she told STAT in an interview for the Nature paper. “Without a screen, kids would move around like they were bored, but with a smartphone, they literally wouldn’t move at all.”
Tackling obesity more broadly is a local issue, she says.
“It’s hard to dismantle all the manufacturing infrastructure that’s been built around ultra-processed foods,” she says, which is important for people who don’t have a steady income. “It will take a long time to make these resources available for healthier foods and less available for unhealthy foods.”
Baylor’s Allison, meanwhile, questioned the paper’s global velocity premise.
“If someone were to say that different populations would have different rates of change because places are different and different in many ways, some of which affect obesity rates, and the changes happening in those places are different, wouldn’t it be shocking if that were not the case?”
Differences between countries include genetics, lifestyle, climate, political environment, economic situation and each country’s demographics, all of which are contributing to changes in obesity, Allison said.
As for the stagnation in high-income countries, “I would say that’s encouraging,” Dietz said. Currently at George Washington University, he previously served as Director of the Division of Nutrition, Physical Activity, and Obesity at the National Center for Chronic Disease Prevention and Health Promotion at the Centers for Disease Control and Prevention. He expressed concern about countries where obesity levels are still rising rapidly.
“The question then becomes why. What is changing in these countries? Is there an increased reliance on cheap and widely available fast food and ultra-processed foods? That’s a question worth answering.”
In a 2018 Lancet paper, Dietz and his co-authors looked at the 1970s U.S. Farm Bill, which spurred rapid increases in food production and subsequent expansion of the food portion. Accelerating the marketing, availability, and affordability of energy-dense foods. Additionally, newer, cheaper, and more potent sweeteners are being added, such as high fructose corn syrup.
“There is some universality to these revelations,” he says.
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