By Nina Agrawal The New York Times Nearly three-quarters of U.S. adults are overweight or obese, according to a sweeping new study. The findings have wide-reaching implications for the nation’s health and medical costs as it faces a growing burden of weight-related diseases. The study, published Nov. 14 in The Lancet, reveals the striking rise of obesity rates nationwide since 1990 — when just over half of adults were overweight or obese — and shows how more people are becoming overweight or obese at younger ages than in the past. Both conditions can raise the risk of diabetes, high blood pressure and heart disease, and shorten life expectancy. The study’s authors documented increases in the rates of overweight and obesity across ages. They were particularly alarmed by the steep rise among children, more than 1 in 3 of whom are now overweight or obese. Without aggressive intervention, they forecast, the number of overweight and obese people will continue to go up — reaching nearly 260 million people in 2050. “I would consider it an epidemic,” said Marie Ng, who is an affiliate associate professor at the Institute for Health Metrics and Evaluation at the University of Washington School of Medicine and a co-author of the new paper. Ng and her co-authors wrote that existing policies have failed to do enough to address the crisis, adding that “major reform” was needed to prevent it from worsening. “It’s going to require a lot more attention and a lot more investment than we are currently giving the problem,” said Dr. Sarah Armstrong, a professor of pediatrics and population health sciences at Duke University who was not involved in the study. The paper defined “overweight” adults as those who were age 25 or over with a body mass index at or over 25, and “obese” adults as those with a BMI at or over 30. The authors acknowledged that BMI is an imperfect measure that may not capture variations in body structure across the population. But from a scientific perspective, experts said, BMI is correlated with other measures of body fat and is a practical tool for studying it at a population level. The authors found a steady increase in the share of people who are overweight or obese over the past three decades. The rate of obesity in particular rose steeply, doubling in adults between 1990 and 2021 to more than 40% — and nearly tripling, to 29%, among girls and women aged 15 to 24. The implications are serious: A Joint Economic Committee Republicans report released this year predicted that obesity will result in up to $9.1 trillion in excess medical expenditures over the next 10 years. Obesity increases the likelihood of numerous metabolic conditions and their associated complications, including high blood pressure, Type 2 diabetes, liver disease, kidney disease, heart attack and stroke. It is also linked to infertility, cancer and poorer mental health outcomes. The report comes as the scientific understanding of what causes obesity, and how best to treat it, is evolving. While the prevailing viewpoint once was that obesity was merely a problem of calories in and calories out, and that people simply needed to eat less and exercise more to lose weight, the reality is much more nuanced, Armstrong said. “Obesity comes from genetic, physiological and environmental interactions,” she said. “It’s not the fault of any one individual who has the disease.” There are many potential drivers behind the skyrocketing rates, including the wide availability of ultraprocessed foods, the challenges to accessing fresh fruits and vegetables and an increase in sedentary online activity. More research is needed to understand the potential effect of environmental factors, like exposure to microplastics that may be disrupting our microbiomes, Armstrong said. Many social drivers of health outcomes, like food insecurity, access to transportation, income, employment and level of education, also play a role, she said — especially for Black, Hispanic, Indigenous and low-income people, who experience obesity at higher rates than white and middle-class people do. The sheer volume of factors is also what makes it so challenging to address. “We recognize a lot is beyond the individual and beyond what can happen in the exam room,” said Dr. Sarah Hampl, a professor of pediatrics at Children’s Mercy Kansas City and the University of Missouri-Kansas City School of Medicine. More than 1 in 3 children are overweight or obese, the study found, and at risk of developing health problems that include high blood pressure, high cholesterol, Type 2 diabetes and fat in the liver. (Adobe Stock) Concerns over children The increasing share of adolescents with obesity are of particular concern, experts said. Almost half of all U.S. teens and young adults — ages 15 to 24 — now are either overweight or obese, compared with 29% in 1990. Children who have obesity are more likely to develop high blood pressure, high cholesterol that leads to plaque buildup in their arteries, Type 2 diabetes and fat in the liver that causes inflammation. “We’re seeing these things more and more commonly emerge even while children are still children,” Armstrong said. These children are more likely to have obesity and related chronic conditions in adulthood, said Dr. Emily D’Agostino, who is a professor of orthopedics and a social epidemiologist at Duke. The research documented a particularly steep rise in obesity rates — reaching 29% in 2021, up from 10% in 1990 — among girls and young women 15 to 24. Hampl said these findings are concerning both for young women themselves and for their potential future children. High maternal BMI before conception, excessive weight gain during pregnancy and high infant birth weight have all been shown to increase the risk of obesity in childhood. Beyond the individual At the individual level, Hampl said, addressing obesity might take a combination of lifestyle modification, medication and surgery — though not every patient will need all of those things. One challenge, she said, is limited insurance coverage for treatments that are known to work — like intensive health behavior and lifestyle treatment as well as weight-loss medications and bariatric surgery. Newer GLP-1 drugs, like Wegovy and Zepbound, are promising, but their long-term effects have yet to be studied, Ng said. In order to have a public health impact, she said, these drugs will need to be widely accessible — a tall order given how expensive they currently are. “It’s not going to be the magic silver bullet to address the problem,” Ng said. Structural changes are needed to reverse population-wide trends, she said, pointing to subsidies for healthy foods and taxes on sugar-sweetened beverages as examples of local or state policies that would have a clear impact on diets. More regulation of nutritional content in foods, and on the marketing of unhealthy foods, could also have an effect, Ng said, but would require coordination at the federal level. Obesity rates are now reaching a saturation point, with the magnitude of the increases slowing down, Ng said. “If you think about if it’s reaching 80% in adults,” she said, “then there really isn’t that much you can go further.”