PNAS: Obesity Linked Not to Sedentary Lifestyle, but to Consumption of Ultra-Processed Foods

A new study published in the journal PNAS challenges the widely held belief that a sedentary lifestyle is the main cause of obesity.

Researchers led by Amanda McGrosey analyzed data from 4,213 individuals across 34 populations on six continents — from hunter-gatherers to residents of industrialized countries.

They examined total energy expenditure (TEE), activity energy expenditure (AEE), basal energy expenditure (BEE), body fat percentage, and body mass index (BMI).

After adjusting for age, sex, and body composition, the study found that AEE — a measure of physical activity — was actually higher in more developed countries than in less developed ones. However, obesity rates were also higher in these countries.

The main conclusion: energy expenditure is only weakly associated with obesity — accounting for about 10% of cases. The key factor, according to the researchers, is the excessive consumption of ultra-processed foods (UPFs) such as sausages, ready-made meals, sugary snacks, and similar products. The proportion of UPFs in the diet directly correlates with body fat levels.

UPFs are high in calories and have a taste and composition that disrupt the natural feeling of fullness, encouraging overeating. Their processing also increases the body’s absorption of calories.

While physical activity remains important for overall health, the researchers emphasize that fighting obesity requires a change in dietary habits and a reduction in the consumption of UPFs.

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