Global obesity rates have more than tripled since 1975. What was once relatively uncommon has become one of the defining health challenges worldwide, with roughly 1 in 7 people now living with obesity and rates still climbing in nearly every country. The increase has been steeper in some populations than others, and the most extreme forms of obesity are growing fastest of all.
Global Rates Since 1975
In 1975, about 6.6% of women and 3% of men worldwide had obesity. By 2022, those numbers had reached 18.5% and 14%, respectively. That means obesity nearly tripled among women and quadrupled among men over roughly five decades. The shift happened across every region, though the pace varied by country and income level.
The increase among children and adolescents has been even more dramatic. In 1975, just 4% of young people aged 5 to 19 were overweight or obese. By 2022, that figure had climbed to nearly 20%. Obesity specifically (not just overweight) increased tenfold in this age group, rising from under 1% of girls and boys to about 7% of girls and 9% of boys.
The United States: A Closer Look
The U.S. has consistently had some of the highest obesity rates among wealthy nations, and the trend has shown no sign of reversing. Obesity prevalence among American adults rose steadily from 1999 through 2018. The most recent federal data, covering August 2021 through August 2023, puts adult obesity at 40.3%. That means two out of every five American adults now meet the clinical threshold for obesity, which is a BMI of 30 or higher.
What’s particularly striking is how the most severe forms of obesity have grown. Since the mid-1980s, the number of U.S. adults with a BMI over 30 has more than doubled. But the number with a BMI over 40 (sometimes called extreme or Class III obesity) has increased fourfold. And those with a BMI over 50 have seen a tenfold increase. The heavier end of the spectrum is expanding much faster than the middle, which carries significant implications for healthcare systems because the health risks associated with obesity rise sharply at higher BMI levels.
How Obesity Classes Break Down
Obesity isn’t a single category. It’s divided into three classes based on BMI:
- Class I: BMI of 30 to 34.9
- Class II: BMI of 35 to 39.9
- Class III: BMI of 40 or higher
For reference, overweight is defined as a BMI of 25 to 29.9. A person who is 5’9″ would cross into Class I obesity at about 203 pounds and into Class III at roughly 271 pounds. These thresholds matter because the risk of conditions like type 2 diabetes, heart disease, and joint problems increases with each class, and Class III obesity is associated with the greatest reduction in life expectancy.
Children Are Following the Same Trajectory
The childhood numbers deserve special attention because they signal what adult obesity rates will look like in the coming decades. Globally, obesity among children and adolescents tripled from about 2% in 1990 to nearly 7% by 2021, with 174 million young people living with obesity that year. In wealthier countries, the rates are considerably higher, and in some nations, more than a quarter of children are already overweight or obese before they reach adulthood.
Children who develop obesity tend to carry it into their adult years. This means the current generation of young people is likely to experience obesity-related health problems earlier in life than their parents did, and for a longer portion of their lives overall.
Where Rates Are Headed
Projections from the World Obesity Federation paint a sobering picture. If current trends continue, more than half the global population (51%, or over 4 billion people) will be living with overweight or obesity by 2035. At that point, 1 in 4 people worldwide will have obesity specifically, up from 1 in 7 today. The Institute for Health Metrics and Evaluation has projected similar numbers through 2050, estimating that more than half of adults and a third of children will be affected.
These aren’t inevitable outcomes. They’re based on what happens if nothing changes. But reversing a trend this large and this entrenched across so many countries has proven extraordinarily difficult. No nation has successfully reduced its obesity rate at the population level once it reached the levels now seen in the U.S., U.K., or Gulf states.
The Economic Weight of the Trend
Rising obesity carries an enormous financial cost. In 2019, the economic impact of overweight and obesity was estimated at 2.19% of global GDP. That includes direct healthcare spending, lost productivity, and disability. The burden isn’t distributed evenly: it averaged about $20 per person in Africa compared to $872 per person in the Americas, and $6 per person in low-income countries compared to $1,110 in high-income ones.
If obesity continues rising at its current pace, those costs are projected to reach 3.29% of global GDP by 2060. Even modest progress could make a significant difference. Reducing the projected rise in obesity by just 5% per year would save an estimated $429 billion annually worldwide. Holding obesity rates at 2019 levels, without any further increase, would save roughly $2.2 trillion per year globally between 2020 and 2060.
Why the Increase Has Been So Steep
No single factor explains a tripling of global obesity in under 50 years. The shift reflects changes in food environments, physical activity patterns, and economic development that occurred simultaneously across much of the world. Highly processed, calorie-dense foods became cheaper and more accessible. Jobs became more sedentary. Commutes got longer. Portion sizes grew. In many developing countries, these changes happened within a single generation as economies urbanized rapidly.
The speed of the increase rules out genetics as a primary driver, since human DNA hasn’t changed meaningfully in this timeframe. Instead, the same genetic predispositions that always existed are now interacting with environments that make weight gain far easier and weight loss far harder. The result is a global shift in average body weight that shows up most visibly in the obesity statistics but extends across the entire population distribution.