Don’t call it the “obesity pandemic.” That one-size-fits-all label no longer captures the diverse trajectories of weight gain around the world, a new report argues. In some countries rising obesity rates are slowing or even sliding downward, trajectories largely linked to the wealth of nations.
Looking instead at velocity to see not how far, but how fast obesity is rising — or not — revealed rates that continue to climb in most low- and middle-income countries, but are flattening in most high-income countries and possibly declining in a few of those more prosperous places.
“The rise is not inevitable,” Majid Ezzati, a professor in the School of Public Health at Imperial College London and academic director of the health collaboration Imperial Global Ghana, said in a media briefing Tuesday. Leader of the new study, he also acknowledged the progress yet to be made in most of the world.
“In the vast majority of low- and middle income countries, it’s going up steadily or even accelerating,” he said. “Some of these levels have surpassed the ones with high-income countries.”
Viewing obesity through this lens elicited some mixed reactions.
William Dietz, professor of exercise and nutritional sciences at George Washington University School of Public Health, told STAT he was puzzled by the “odd approach” of looking at trajectories based on year-to-year changes in body mass index (BMI) or obesity prevalence, making it hard to interpret.
David Allison, chief of the Division of Nutrition in the Department of Pediatrics at Baylor College of Medicine, told STAT, “If one conclusion is obesity went up a lot in many places and continues to go up in most places, that’s not news.”
The study authors said their approach reveals useful points for comparison, for example, spotlighting outliers like the United States.
In the U.S., obesity has hit a plateau in children and adolescents, but rates are still climbing for adults, if not as fast as before, the paper said. While that may be a promising trend, obesity rates in the U.S. still rank among the highest in the world, and No. 1 among high-income Western countries. American obesity ranges from 20% to 23% for girls and boys and from 40% to 43% for women and men. In Japan, rates are in the single digits for all: 3% to 7% for girls and boys and 4% to 8% for women and men.
Worldwide, the velocity of obesity was greater in 2024 than any other year over the 45-year period for women in 84 of 200 countries, and for men in 109 of 200 countries, the authors wrote in a paper published Wednesday in Nature.
“We have a diversity of trajectories across countries,” Ezzati said. “This diversity exists even across countries that have really similar economic, environmental, technological features. The surprise to me is how much more work we have to do to dig into what’s underlying some of these differences.”
The analysis tracked obesity prevalence as measured by BMI from 1980 through 2024. The authors belong to the NCD Risk Factor Collaboration, an international group of 2,000 scientists following noncommunicable diseases. They drew on a database of height and weight among 232 million participants in more than 4,000 population-based studies around the world.
They found that increasing obesity rates have leveled off in most high-income countries. Rates appear to be declining in France, Italy, and Portugal, but it’s too soon to tell if that’s a durable change.
It’s also too soon to see what effect obesity drugs might have, the study authors said.
“As there’s a greater uptake of these obesity management medications, there could be potentially in the future an effect on the trend. But I think the really important thing is we don’t lose sight of the importance of prevention,” co-author Jennifer Baker, president-elect of the European Association for the Study of Obesity, said at the media briefing. “Maybe if we come back five to 10 years from right now, we will see something quite different.”
The reasons rates differ vary by country. The Nature paper didn’t set out to establish cause and effect, but Ezzati alluded to research from others on possible factors to explain why obesity rates are rising in some places and tempered in others.
After World War II, the advent of industrial food and commercial food allowed people to have fruits and vegetables year-round. It also made it easier to eat foods both good and bad. Later, knowledge about obesity helped people to select something healthy to eat, allowing obesity rates to moderate and even plateau, especially where institutions supported healthy choices.
In India and other Asian countries, there is no plateau, study co-author R. Guha Pradeepa of Madras University said at the briefing, but an acceleration of obesity.
She pointed to economic growth and rapid urbanization, which has limited space for walking, cycling, or even playing. Then there’s the food.
“In the low socioeconomic countries, you can see that there is a rapid shift from traditional food, away from diets rich in whole grains, vegetables, and legumes, and towards energy-dense processed food which are high in refined cereals, added sugars, salt, and saturated fats,” she said at the briefing.
Carolyn Bramante, an assistant professor of medicine in the University of Minnesota Medical School who provides care for and researches adult and pediatric obesity, cited a growing appreciation for two exposures in children that she sees in her practice: sleep and screen time.
“Screen use disrupts sleep, and it also removes a lot of neat non-exercise active thermogenesis that happens throughout the day,” she told STAT in an interview about the Nature paper. “Without a screen, they’re doing all those little bored kid movements, but with a phone, they just are literally not moving their body at all.”
Addressing obesity more widely is a regional question, she said.
“It’s hard to unwind all the manufacturing infrastructure that has been built around ultra-processed foods,” she said, which is significant for people who don’t have a secure income. “It will take a long time to shift those resources into making more healthy things available and not making unhealthy foods available.”
Meanwhile, Baylor’s Allison questioned the paper’s global velocity premise.
“If somebody said places differ and they differ in many ways, some of which will also affect obesity rates and changes going on in those places differ so that the rates of change are going to differ in different populations, wouldn’t it be shocking if that wasn’t the case?”
The ways countries vary include genetics, lifestyles, climate, the political environment, the economics, and the demographics of every country, Allison said, all of which contribute to changes in obesity.
As for the plateau in high-income countries, “I would say it’s encouraging,” said Dietz, now at George Washington but previously director of the Division of Nutrition, Physical Activity, and Obesity in the National Center for Chronic Disease Prevention and Health Promotion at the Centers for Disease Control and Prevention. He expressed concern about those countries where obesity levels are still soaring.
“That begs the question, why. What is it that’s changing in those countries? Is it more reliance on fast food and ultra-processed foods, which are inexpensive and widely available? That’s a question worth answering.”
In a 2018 Lancet paper, Dietz and his co-authors singled out U.S. farm bills in the 1970s that fueled a rapid increase in food production followed by larger food portions; accelerated marketing, availability, and affordability of energy-dense foods; plus new cheap and potent sweetening agents, such as high-fructose corn syrup.
“There’s some universality to these exposures,” he said.
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