People who consume ultra-processed foods consume more calories and gain more weight than when their diet was poorly processed, according to findings from a National Institutes of Health study. The difference came even though the meals provided to volunteers in both ultra-processed and minimally processed diets contained the same number of calories and macronutrients. The results were published in Cell metabolism.
This small-scale study of 20 adult volunteers, conducted by researchers at the National Institute of Diabetes, Diseases of the Digestive System and Kidneys (NIDDK) of the NIH, is the first randomized controlled trial examining the effects of ultra foods. -transformed as defined by the NOVA classification system. . This system considers foods as "ultra-processed" if they contain ingredients primarily used in the manufacture of industrial foods, such as hydrogenated oils, high fructose corn syrup, flavoring agents and emulsifiers.
Previous observational studies of large groups of people have shown associations between diets rich in processed foods and health problems. But since none of the previous studies randomly assigned people to eat specific foods and then measured their results, scientists could not say for sure if processed foods were a problem in themselves or if people ate them. had health problems for other reasons, such as lack of access to fresh foods.
"Although we looked at a small group, the results of this tightly controlled experiment showed a clear and consistent difference between the two regimens," said Kevin D. Hall, Ph.D., NIDDK principal investigator and lead author of l & # 39; study. "This is the first study to demonstrate causality: ultra-processed foods cause people to consume too many calories and gain weight."
For the study, the researchers admitted 20 healthy adult volunteers, 10 men and 10 women, to the NIH Clinical Center for a continuous month and, in random order for two weeks for each diet, provided them with compound meals. ultra-processed foods or low-processed food meals. For example, an ultra-processed breakfast may consist of a bagel with cream cheese and turkey bacon, while the unprocessed breakfast consisted of oatmeal flakes with bananas, walnuts and skimmed milk.
Ultra-processed and unprocessed meals contained the same amounts of calories, sugars, fiber, fat and carbohydrates, and participants could eat as much or as little as they wanted.
In the ultra-processed diet, people ate about 500 more calories a day than during an unprocessed diet. They also ate faster with the ultra-processed diet and gained weight, while they lost weight with the unprocessed diet. Participants, on average, took 0.9 kg, or 2 pounds, while they were on an ultra-processed diet and lost an equivalent amount with the unprocessed diet.
"We need to determine what specific aspect of the ultra-processed food has affected people's eating behavior and has led to weight gain," said Hall. "The next step is to design similar studies with an ultra-reformed diet reformulated to see if the changes made can remove the effect of diet on calorie intake and weight body. "
For example, slight differences in protein levels between ultra-processed and unprocessed diets in this study could potentially account for up to half of the difference in caloric intake.
"Over time, extra calories add up and this extra weight can lead to serious health problems," said Griffin P. Rodgers, MD, director of NIDDK. "Such research is an important element in understanding the role of nutrition in health and can also help people identify foods that are both nutritious and accessible, which helps them stay healthy in the long term."
Although the study reinforces the benefits of unprocessed foods, the researchers note that it can be difficult to limit ultra-processed foods. "We need to be aware that it takes longer and more money to prepare less processed foods," Hall said. "Telling people to eat healthier may not be effective for some people without better access to healthy foods."
Support for the study was mainly provided by the NIDDK Intramural Research Division.