A new global study shows that the real reason for rising obesity isn’t that people have stopped moving — it’s that they’re eating too much, especially the wrong kinds of food.
Researchers looked at data from over 4,000 adults across 34 different groups, from remote hunter-gatherers to office workers in big cities. Surprisingly, people in wealthier countries burned more calories on average than those in less developed areas. But they also had much higher levels of body fat.
The study, published in the Proceedings of the National Academy of Sciences, used one of the most accurate methods available to measure how many calories people burn each day. Even with more movement and energy burned, people in rich nations were gaining more weight — and the biggest difference came down to what was on their plates.
Ultra-processed foods, packed with empty calories and engineered to be overeaten, were the main culprit.
“Our analyses suggest that increased energy intake has been roughly 10 times more important than declining activity rates in driving the modern obesity crisis,” the researchers concluded.
Amanda McGrosky of Elon University and Amy Luke of Loyola University noted that across all populations, energy burn was strikingly similar once adjusted for body size. In fact, individuals in economically developed countries often burn more calories because they weigh more — and heavier bodies naturally require more energy.
Dr. Brett Osborn, a Florida neurosurgeon and longevity expert who was not involved in the study, put it bluntly: “We’re not gaining weight because we stopped moving. We’re gaining because we’re overfed.” He criticized the modern food supply as being loaded with what he called “nutrient-void products” that are marketed as healthy or convenient but are contributing to mass weight gain.
These foods — known as ultra-processed foods — include sugary drinks, packaged snacks, and ready-made meals. They are often engineered to be highly palatable and easy to digest, leading the body to absorb more calories while feeling less full. Osborn warned that such foods override natural hunger signals and promote fat storage while fueling inflammation.
Lindsay Allen, a Florida-based registered dietitian, added that muscle mass and stress levels also play a role. “Having sufficient muscle is what drastically improves metabolism and fat-burning capabilities,” she said, noting that chronic stress can interfere with metabolism by keeping the body in “survival mode.”
The study’s implications challenge long-standing public health messaging that centers on the slogan “eat less, move more.” While regular exercise remains crucial for heart health, mental well-being, and overall longevity, the researchers emphasized that focusing solely on activity misses the bigger picture.
“Increasing energy intake has vastly outpaced any changes in physical activity,” said McGrosky and Luke. “If you’re worried about excess body fat, focus on calories in. It’s much harder to meaningfully increase how many calories you burn than it is to reduce how many you consume.”
In other words, obesity is less about sloth and more about what’s being served at the dinner table.
For many Americans who’ve watched health officials blame screen time and desk jobs for the nation’s weight crisis, this study offers a different explanation — one that points to the food industry’s role in flooding the market with processed, calorie-dense options that are hard to resist and easy to overeat.
Osborn said it’s time to drop the myth that laziness is the culprit. “It’s the constant stream of ultraprocessed, nutrient-void products being shoveled into mouths under the guise of health or convenience. And it’s killing us — slowly, predictably and en masse.”