Nearly three quarters of US 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.

(Robert F. Kennedy Jr, President-elect Donald Trump’s pick for health secretary, has indicated his priorities include addressing what he calls the “chronic disease epidemic” of conditions including obesity, diabetes and autism, and reducing chemicals in food, a Reuters report on Thursday said.

Kennedy had in September criticised a New York Times opinion article about the weight loss drug Ozempic, saying: “Instead of fixing our food system and addressing the obesity crisis at its root, the author focuses on a drug that may palliate the
symptom — and gladden the wallets of distant Big Pharma execs.”

Kennedy has also falsely linked vaccines to autism and erroneously claimed that fluoride, which helps reduce tooth decay, is associated with bone fractures and cancer.)

The study, published on Thursday 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 one in three 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.

Dr 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 paediatrics 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 and 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 body mass index (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 per cent — and nearly tripling, to 29 per cent, 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, Dr 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 ultra-processed 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, Dr 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 increasing share of adolescents with obesity is of particular concern, experts said. Almost half of all US teens and young adults — ages 15 to 24 — now are either overweight or obese, compared with 29 per cent in 1990.

Children who have obesity are more likely to develop high blood pressure, high cholesterol that leads to plaque build-up in their arteries, Type 2 diabetes and fat in the liver that causes inflammation.

The research documented a particularly steep rise in obesity rates — reaching 29 per cent in 2021, up from 10 per cent in 1990 — among girls and young women 15 to 24.

New York Times News Service