Does ultra-processed food make you eat more calories?

The difference between packaged food and a meal cooked at home is not only taste. At the NIH Clinical Center, researchers kept people on the ward and changed how processed the food was, then let them eat as much as they wanted.

What the study looked at

Kevin Hall and colleagues admitted 20 weight-stable adults in 2019. Their mean age was 31.2 years, and their mean BMI was 27.

The order was randomized. Two weeks were ultra-processed, then two weeks were a minimally processed diet, or the reverse. People could eat less or more than they were offered.

The meals put in front of them were matched. Presented calories, energy density, carbohydrate, protein, fat, sugar, sodium, and fiber were similar on both diets. The difference was close to “was this made from ultra-processed foods?”

Results

During the ultra-processed two weeks, energy intake was 508 kcal/day higher (SE 106, p = 0.0001). The extra came from carbohydrate (280 kcal) and fat (230 kcal). Protein barely moved (−2 kcal, p = 0.85).

Weight change tracked how much people ate (r = 0.8). They gained 0.9 kg on the ultra-processed diet (p = 0.009) and lost 0.9 kg on the unprocessed diet (p = 0.007). Figures are mean ± SE.

Limits

Twenty people, two weeks each, eating food served on a ward. The trial does not recreate a work lunch, a dinner out, or a convenience-store run. It does not show that the same difference appears at home.

A served ultra-processed meal was not higher in calories than the other plate. The researchers matched that, and people then ate more of the ultra-processed food. That is a different question from the number printed on a package.

What this means for a log

The word “ultra-processed” does not raise or lower a calorie count by itself. In this study, the difference was how much people actually ate. If a photo misses sauce, a drink, or an extra bite, that difference disappears from the log too.