Same Calories, Different Effects on Metabolism

A randomized, controlled study examined whether processing changes the body’s reaction to nutritionally similar food. Researchers enrolled 57 adults. Among them, 32 ate two matched meals on different days: one was ultraprocessed, while the other used less-processed food. The meals were closely aligned for calories, protein, carbohydrates, fat, fiber, sodium, water, and glycemic index.

Both meals produced comparable blood sugar patterns, but insulin rose more and remained elevated longer following the ultraprocessed option. The body’s choice of fuel also shifted. Carbohydrate use increased more with the less-processed meal, whereas fat burning was greater with the ultraprocessed one. That meal also produced a greater overall metabolic rate.

The study included brain imaging as participants looked at food pictures and reported what they would pay for each item. For those who completed both parts of the research, changes in carbohydrate use corresponded with changes in brain responses to the images. Brain activity also related differently to the amounts participants would pay for ultraprocessed versus less-processed options, although neither category was consciously judged more appealing.

Processing can alter food’s physical form and therefore how digestion breaks it apart. The findings indicate that matching nutrition labels does not necessarily produce matching metabolic or brain responses. Because the study was relatively small and measured short-term effects, further research is needed to establish whether these differences influence health over time.