Nature Metabolism: Ultra-Processed Food Makes the Body Use Energy Differently

Ultra-processed foods are products that undergo multiple stages of industrial processing and typically contain additives rarely used in home cooking. Their share of the diet is increasing: in the United States, they already account for more than half of all calories consumed. Higher consumption of ultra-processed foods has also been associated with an increased risk of cardiovascular and metabolic disorders, although this association alone does not establish a cause-and-effect relationship.

The new study involved 57 people, with data from 32 participants used for the main metabolic analyses. They were given two small meals of approximately 300 kilocalories each: one consisting of ultra-processed foods and the other of minimally processed foods. The meals were closely matched for calories, protein, fat, carbohydrates, fiber, sodium, water, energy density, and glycemic index.

Despite these similarities, the body responded differently to the two meals. Insulin levels were noticeably higher for several hours after participants ate the ultra-processed meal. Overall changes in blood glucose levels were similar, although glucose rose more quickly after the minimally processed meal and remained elevated for longer after the ultra-processed one.

The body's use of energy sources also differed. After the minimally processed meal, the use of carbohydrates as fuel increased more substantially. Following the ultra-processed meal, this shift was less pronounced, and the body relied relatively more on fat. The researchers note that this pattern resembles certain features of impaired metabolism, but the experiment did not show that ultra-processed food causes insulin resistance or diabetes.

Interesting differences also emerged in the brain scans. Participants underwent MRI while viewing images of familiar foods. Those who showed greater differences in the rate of carbohydrate use after the two types of meals also exhibited differences in activity in certain brain regions involved in sensory processing, learning, and the reward system.

However, participants did not show an obvious preference for ultra-processed foods. They rated their willingness to buy products from the two categories similarly, although they considered ultra-processed foods less healthy. Thus, the study does not support the idea that such foods automatically provide greater pleasure or are inherently more appealing.

The researchers suggest that the physical structure of food, not just its chemical composition, may be important. Industrial processing can alter how quickly food breaks down during chewing and how its nutrients are released and absorbed. This, in turn, may change the signals sent from the gut to the brain after eating.

The authors emphasize, however, that the study has several limitations. It was small, the participants were healthy adults of normal weight, and each meal contained only about 300 kilocalories.

In addition, the meals differed not only in their degree of processing but also in some ingredients and protein sources. As a result, the researchers could not fully separate the effects of processing itself from those of food composition.