Obesity's primary driver? A new PNAS study upends a popular myth

Exploring what fuels obesity

According to НВ — Техно: With global obesity rates continuing to climb, an international team of scientists has cast doubt on the widely repeated claim that a lack of movement is the main cause of the obesity epidemic. In a paper published in PNAS on 28 August 2023, researchers led by Professor Herman Pontzer of Duke University compared the daily energy expenditure of 4,200 adults-both men and women-across 34 countries.

The participants came from strikingly different backgrounds, ranging from Hadza hunter-gatherers in Tanzania to office employees in Europe and the United States. To measure daily energy burn, each person drank specially labeled water containing safe isotopes, which were later tracked through urine samples. Once the numbers were adjusted for body size, the daily calories burned by hunter-gatherers and sedentary desk workers turned out to be nearly identical.

How food choices shape body weight

The authors explain that human metabolism works on a compensatory principle: when someone burns extra energy through exercise, the body trims energy used for internal functions. Epidemiologists from Harvard and Tufts University emphasize that the real engine behind weight gain has been the changing composition of the food supply, not simply physical inactivity. People whose diets delivered a larger share of calories from ultra-processed foods had noticeably higher amounts of body fat.

These findings challenge long-standing assumptions about obesity. In nineteenth-century America, being overweight was rare, yet over the past hundred years it has become a widespread epidemic in developed nations. Exercise is still important for preventing illness, supporting mental health, and increasing longevity, but the researchers insist that training alone cannot undo the damage caused by a poor diet.

Pontzer's work offers a new way of thinking about obesity, placing nutrition at the center of prevention efforts.

As obesity becomes an ever more urgent public health issue, this research could guide future recommendations on diet and exercise. Redirecting attention from activity levels toward dietary patterns may encourage fresh approaches to tackling the epidemic, reminding us that both calorie count and calorie quality matter for the health of populations.

As researchers delve deeper into the complexities of weight management, the impact of dietary habits becomes increasingly evident. A recent study highlights how an 8-hour eating window may enhance cognitive functions in older adults, further emphasizing the intricate relationship between food intake and overall health. Understanding these connections can provide valuable insights into effective strategies for tackling obesity.