After an ultra-processed diet, 20-year-olds eat more calories, even if they’re not hungry. Scientists: make healthy foods accessible.

Two weeks of meals based on ultra-processed foods are enough to change the way young adults eat. According to a study that investigated the effects of a diet saturated with industrial and hyper-processed foods, rich in additives and colorings, on American children, after 15 days of this diet, the desire for caloric foods increases among 18-21 year olds, even when they are not really hungry. A drive that can open the doors to obesity, a disease that could affect one in three young Americans by 2050.

The research, funded by the US National Institutes of Health, was published in the scientific journal Obesity.

Diet comparison

Scientists at Virginia Tech recruited 27 girls and boys between the ages of 18 and 25 who fed for two weeks in two opposite ways: in one case, with a diet based 81% on ultra-processed foods, such as packaged sweet and savory snacks, cereals, flavored drinks and fruit yogurt, in the other with simple and unprocessed products such as plain yogurt, vegetables, legumes and dried fruit.

Unlike other studies conducted in the past on ultra-processed subjects, in this one the diets were carefully calibrated to the energy needs of the children so as to keep their weight stable. Furthermore, the two food plans were equivalent in terms of fiber, added sugars, energy density, and as far as possible also in terms of macronutrients, vitamins and minerals.

In this way it was possible to measure the effect of industrial hyper-processing of food, which does not depend closely by the ingredients that the food contains, or in any case not only: the packaging, the manufacturing process, the texture have something to do with it… Furthermore, since the participants did not gain weight during the diet, their energy needs did not change during the study.

The effects on younger people

Each participant followed both diets after a 4-week period in which he returned to normal eating habits, acting as his own control subject.

After two weeks of ultra-processed foods, i.e. rich in aromas and flavors that cannot be reproduced at home or come from industrial manufacturing processes that distort the starting ingredients, the children in the 18-21 year old subgroup consumed more calories when they were placed in front of an “all you can it” buffet, free to choose their own breakfast. Not only that: they chose to try various snacks more often even if they were no longer hungry.

As Alex DiFeliceantonio, one of the authors of the study, an expert in food choice mechanisms, explains: “Snacking when you are not hungry is an important predictive factor of future weight gain in young people, and it seems that exposure to ultra-processed foods increases this tendency in adolescents.”

Among 22-25 year olds, however, the assigned diet had no impact either on the total calories consumed at the buffet, or on the prevalence of ultra-processed foods chosen on that same occasion.

Ultra-processed: a social problem

Future studies will have to ascertain whether the same mechanisms also come into play in children of other age groups: adolescents and young adults are more vulnerable to dietary changes because they find themselves in a period of life in which the habits and contexts in which we eat change. Triggering an addiction to ultraprocessed foods at these ages risks laying the foundations for a future obesity problem.

Simultaneously with the study on Obesity appeared on Lancet a series of reviews on ultra-processed people that takes stock of their diffusion, the damage they cause and the responsibilities for their effects. According to Carlos Monteiro, professor in the Department of Nutrition at the School of Public Health at the University of São Paulo in Brazil and founder of studies on ultra-processed foods, as well as the classification system to distinguish them from other foods, “ultra-processed foods are reshaping diets around the world, replacing fresh and minimally processed foods and meals.”

According to Monteiro and colleagues, these foods are worsening the quality of nutrition, promoting excess food intake and contact with dangerous chemical additives. Furthermore, they contribute to the spread of many chronic diseases, such as type 2 diabetes, obesity, cardiovascular problems, depression, as well as being increasingly associated with early death from any cause.

It’s not an individual problem

The authors underline that the responsibility for making different food choices cannot be placed on individuals, who are forced to put cheap, highly advertised foods in their shopping carts, specifically designed to be easy to consume and indispensable, once they have started eating them.

Coordinated health policies are needed to reduce the production, marketing and consumption of ultra-processed foods, to be reported to consumers with specific labels; at the same time it is urgent to improve access to healthy alternatives, which must be made economical and easy to find in every context (starting from schools, as has been done in Brazil: in the country, from 2026, 90% of the food in school canteens must be fresh and minimally processed).