Study Finds Diet, Especially Ultraprocessed Foods, Plays Major Role in Obesity
In a groundbreaking study that challenges long-held assumptions about the causes of obesity, researchers have found that diet — particularly the consumption of ultraprocessed foods — plays a significantly greater role than physical activity in contributing to weight gain. The study, involving over 4,000 adults from 34 diverse populations, including hunter-gatherer communities and office workers, revealed that differences in body fat among individuals were largely due to calorie intake rather than activity levels. While physical exercise is crucial for overall health, the researchers emphasize that the primary driver of obesity is the number of calories consumed, especially from calorie-dense, highly palatable processed foods.
The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), analyzed total energy expenditure (TEE) and compared it with body fat percentage and BMI. The findings show that people across all lifestyles and income levels burned similar amounts of energy, even if their daily routines differed dramatically. The researchers noted that the differences in body fat were not primarily due to activity levels or total daily energy burned, but rather an excess of calories consumed.
Ultraprocessed foods, which have long ingredient lists and are often calorie-dense, shelf-stable, and highly palatable, were identified as a major contributor to the global obesity crisis. These foods are engineered to override satiety signals in the brain, making it easier to overeat and harder for the body to eliminate excess energy. The study authors predict that as more populations are exposed to these foods, obesity rates in regions with lower current rates are likely to rise.
Experts like Dr. Brett Osborn, a Florida neurosurgeon and longevity expert, agree with the study’s findings, stating that ‘you can’t out-train a bad diet.’ Osborn emphasized that while exercise remains important for cardiovascular health and mental well-being, the key to combating obesity lies in reducing calorie intake, especially from ultraprocessed foods. He noted that the problem is not laziness or lack of movement, but rather the constant stream of nutrient-void products marketed as healthy or convenient.
Lindsay Allen, a registered dietitian nutritionist, added that muscle mass and stress levels also play a role in metabolism and fat accumulation. She pointed out that people in high-stress societies tend to be fatter due to changes in metabolism caused by stress hormones. Allen recommended focusing on building strength and muscle to improve metabolic rates and fat-burning capabilities, rather than solely focusing on calorie burning through exercise.
The researchers concluded that while physical activity is beneficial, it is the excessive consumption of calories — particularly from ultraprocessed foods — that has driven the modern obesity crisis. They urged individuals to focus on reducing calorie intake, especially over the long term, rather than trying to increase the number of calories burned through exercise.