A study conducted by scientists from the University of Bristol is based on a re-analysis of data collected during an experiment organized by the National Institutes of Health in the USA. In this experiment, participants consumed only natural foods for two weeks, after which they switched to a diet of ultra-processed foods for a similar period. The nutrient composition remained unchanged — fats, salts, sugars, and fiber were identical for both groups.
One of the key findings was that participants consuming unprocessed foods ate significantly more by weight, yet their energy expenditure decreased. The volume of food increased by more than 50%, while daily calorie intake decreased by 300 kcal. This can be explained by the fact that natural foods, rich in vegetables and fruits, have low energy density. The high water and fiber content contributes to quick satiety without overloading the body with excess calories.
In contrast, with ultra-processed foods, even small portions turned out to be high in calories. Industrial food often contains carbohydrates and fats in proportions that stimulate the pleasure centers in the brain, leading to overeating. Additionally, the artificial addition of vitamins allows for the intake of necessary micronutrients from high-calorie products, depriving the body of the need to seek them from low-calorie sources such as vegetables.
Professor Jeff Brunstrom, one of the leading authors of the study, noted that people intuitively make the right choice when offered natural foods. "Our food preferences are not random — in fact, we make more conscious decisions than previously thought when foods are presented in their natural form," he emphasized. Thus, the quality of food is paramount for healthy eating, allowing the body to find a balance between satiety, pleasure, and benefit on its own.
