Obesity: Ultra-Processed Foods in the Diet Lead to Overeating

American scientists have found that teenagers and young adults respond differently to ultra-processed foods. Study participants aged 18–21 consumed significantly more calories after a two-week diet rich in ultra-processed foods, while no such effect was observed in those aged 22–25. The study was published in Obesity.

The analysis relied on data from The Lancet, according to which by 2050, one in three Americans aged 15–24 will meet the criteria for obesity. Although this rise is linked to lifestyle, heredity, and other factors, diet plays a key role. Ultra-processed foods, which account for 55–65% of the diet of young Americans, have previously been associated with metabolic disturbances, poor cardiovascular health, and other problems.

Researchers from Virginia Tech aimed to determine how different types of diets affect eating behavior in a buffet-style setting. They conducted a controlled study involving 27 men and women aged 18–25 whose body weight had remained stable for at least six months.

Volunteers followed one of two diets for two weeks: the first consisted of 81% ultra-processed foods, while the second contained none. The diet was strictly controlled: participants ate breakfast in the lab, and the remaining meals were prepared in a metabolic kitchen. Both diets were carefully matched across 22 parameters — from macronutrients and fiber to mineral composition.

Participants were then invited to a buffet-style breakfast where they could eat as much as they wanted. Each person received a tray totaling about 1,800 kilocalories — four times the size of a standard breakfast. Afterward, researchers assessed their tendency to eat without hunger: volunteers were given a tray of snacks and asked to try each one, then allowed to continue eating if they wished.

Overall, the type of diet did not affect the total number of calories consumed. However, statistically significant differences emerged when participants were divided by age. Among 18–21-year-olds, the diet high in ultra-processed foods increased calorie intake at the buffet, and they were more likely to continue eating even without feeling hungry. This trend was absent among 22–25-year-olds.

In the future, the researchers plan to expand the sample size and use neuroimaging and biomarkers to better understand the mechanisms through which ultra-processed foods influence eating behavior in young people.

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