Obesity rates have risen dramatically over the past several decades, both globally and in the United States. In 1990, 25% of adults worldwide were overweight. By 2022, that figure had climbed to 43%, with 16% of all adults meeting the threshold for obesity. The shift has been even more striking among children, and the forces driving it touch nearly every part of modern life.
The Global Picture Since 1990
The worldwide prevalence of obesity more than doubled between 1990 and 2022. As of that year, over 890 million adults were living with obesity, part of a broader group of 2.5 billion adults classified as overweight. The split between men and women is nearly even: 43% of men and 44% of women were overweight in 2022.
The World Health Organization formally recognized obesity as a global epidemic in 1997, but the trend was already well underway. What makes the recent acceleration notable is its reach. Obesity is no longer concentrated in wealthy Western nations. It has become a worldwide phenomenon, affecting low- and middle-income countries that simultaneously struggle with malnutrition.
How the United States Got to 40%
The U.S. offers the longest and most detailed tracking data, and the numbers tell a stark story. In the early 1960s, about 10.7% of American adults aged 20 to 74 were obese. By the most recent measurement period (August 2021 through August 2023), that figure had reached 40.8% in the same age group. The overall age-adjusted obesity rate for adults 20 and older was 40.3%.
That’s roughly a fourfold increase in six decades. The steepest climb happened between the 1980s and early 2000s, a period that coincided with major changes in food production, portion sizes, and daily activity levels. The rate has continued rising since then, though more gradually.
Children and Adolescents Hit Hardest
The most alarming shift has been among young people. Globally, obesity among children and adolescents aged 5 to 19 quadrupled between 1990 and 2022. The share of kids in that age group who were overweight (including those with obesity) jumped from 8% to 20%. Boys and girls were affected almost equally, at 21% and 19% respectively. In 2024, an estimated 35 million children under the age of 5 were overweight.
This matters because childhood obesity tends to persist into adulthood. A child who is significantly overweight at age 10 faces far higher odds of remaining so at 30. The quadrupling among young people signals that the adult obesity rates of the 2030s and 2040s could be substantially higher than today’s.
What Changed: Food, Work, and Daily Life
No single factor explains the rise. It’s the result of several overlapping shifts that reshaped how people eat, move, and spend their time.
The food supply changed fundamentally. In the U.S., total available calories per person (adjusted for waste) rose 22% between 1970 and 2010, from about 2,054 to 2,501 calories per day. That increase came largely from cheaper, more accessible processed food. Among American children and teens, ultra-processed foods made up 61.4% of total energy intake in 1999-2000 and climbed to 67% by 2017-2018. These foods, which include packaged snacks, sweetened drinks, and ready-to-eat meals, are engineered to be convenient and palatable. They also tend to be calorie-dense while doing a poor job of making you feel full.
At the same time, daily physical activity dropped sharply. The nature of work in the U.S. flipped almost completely over half a century. In 1960, manufacturing and agricultural jobs accounted for 47% of all employment. By 2008, that had fallen to about 20%. Service and office-based jobs rose from 50% to nearly 80% over the same period. That shift alone removed hours of physical exertion from millions of people’s daily routines, and nothing comparable replaced it. Leisure-time exercise, while promoted heavily, has not offset the calories that workplace activity once burned.
The Health Toll Has Tracked the Trend
Rising obesity has brought a parallel surge in related conditions. Type 2 diabetes incidence roughly doubled over the same decades, and the two trends have moved almost in lockstep. When researchers looked at diabetes rates by weight category, the increase was concentrated among people with obesity: prevalence in that group rose from 18.0% to 20.1%, while rates among people at lower weights stayed relatively flat. That pattern strongly suggests obesity itself is the primary driver.
Diabetes diagnosed in children, once almost unheard of for the type 2 form, has become increasingly common. If current trends continue, an estimated one in three Americans could have diabetes by 2050. Heart disease, certain cancers, sleep apnea, joint problems, and fatty liver disease have all risen alongside obesity as well.
Where the Trend Is Heading
Projections from the World Obesity Federation paint a sobering picture for the next decade. By 2035, an estimated 1.53 billion people worldwide will be living with obesity, and another 1.77 billion will be overweight. Combined, that would represent 54% of all adults on the planet.
The economic costs are projected to match the scale of the health burden. Estimates put the global financial impact of obesity at $4.32 trillion per year by 2035, equivalent to about 3% of global GDP. That figure includes direct healthcare spending, lost productivity, and the broader economic drag of a less healthy workforce.
Why the Rise Has Been So Difficult to Reverse
Despite decades of public health campaigns, calorie labeling, school lunch reforms, and widespread awareness that obesity carries serious health risks, population-level rates have continued climbing. The reasons are partly biological and partly structural. The human body evolved to store energy efficiently in environments where food was scarce, and modern food environments exploit that wiring with constant availability of cheap, calorie-dense options.
The structural side is just as powerful. In many communities, the most affordable and accessible foods are the most processed. Walkable neighborhoods, safe parks, and time for physical activity are unevenly distributed across income levels. Work hours in many countries have remained long, leaving less time for cooking and exercise. These conditions don’t make weight gain inevitable for any individual, but across entire populations, they push averages steadily upward. The result is a trend that has resisted reversal in virtually every country where it has taken hold.