Same Healthy-Eating Targets, Slightly More Weight Loss on Less-Processed Food

CATEGORY: DIET & WEIGHT

Matching the nutrition on paper did not make the two diets equal. Both menus in this trial hit the same national healthy-eating targets for fat, sugar, salt and fiber. One was built mostly from minimally processed food, the other mostly from ultra-processed food. Over eight weeks, the minimally processed menu produced about twice as much weight loss.¹ The same fifty people ate both. How food is made, it seems, can move body weight even when the label does not change.

Same Targets, Different Degree of Processing

Ultra-processed foods are assembled largely from industrial ingredients and additives rather than from things you would recognize in a kitchen. Mass-produced packaged bread, reconstituted meat, flavored snacks, sweetened drinks. Minimally processed foods are whole or barely handled: fresh fruit, plain yogurt, eggs, grains cooked at home. The twist in this trial is that both menus were written to meet the same official nutrition targets. Degree of processing was the only large difference between them.

Fifty People Ate Both Diets, Eight Weeks Each

These were not people who picked a diet. Each of the fifty adults was handed both, in an order decided for them, and served as their own comparison. Eight weeks on the minimally processed menu, then eight on the ultra-processed one. A four-week gap sat between them so one phase would not bleed into the next. Both menus were matched to the United Kingdom’s national healthy-eating guide, and the food itself was supplied, which is how the researchers held nutrition steady while varying only processing. The difference in percent weight change between the two diets was named as the main outcome before the trial started.¹ Weight came off a calibrated scale. Body composition, meaning how much of a person’s weight is fat rather than other tissue, was measured on a standard clinic device.

About 2% of Body Weight Against About 1%

On the minimally processed diet, participants lost about 2% of their body weight. On the ultra-processed diet, about 1%.¹ That is roughly double over the same eight weeks, a gap of about one percentage point of body weight, or about 0.96 kilograms more loss on the less-processed menu.¹ Reductions in fat mass and in visceral fat, the fat packed around the internal organs, reached statistical significance only in the minimally processed phase. Participants also reported better control over cravings during that stretch. These are modest amounts across two months, not transformations. Every measure moved the same way.

Physical Form, Chewing, and Two Other Studies

Neither diet was a bad diet. Both followed healthy guidelines and both came with some weight loss, so this is not a case against ultra-processed food as a category. What the trial suggests is that the physical form of food can nudge body weight on its own, independent of the nutrition label. How fast it goes down and how hard it pulls at cravings may be doing work the label never records. The trial was small and short, which makes the result an early signal, and follow-up discussion of it has already been published. A separate randomized crossover study in Japanese men with overweight found something similar. A week of ultra-processed meals left them about 1 kilogram heavier than a matched week of whole-food meals, and they chewed less.² A review pooling studies of nearly 10 million people found higher ultra-processed intake more common among people with obesity, though that kind of research watches what people already eat and cannot show cause.³

Key Takeaways

• Across eight weeks, a mostly minimally processed menu produced roughly twice the weight loss of an ultra-processed one, even though both met the same healthy-eating targets.
• The amounts were modest and the trial was small and short. It is best read as an early signal.
• Because both menus met the same targets, the difference tracked with processing rather than with the nutrition on paper.

References

1. Dicken SJ, Jassil FC, Brown A, et al. Ultraprocessed or minimally processed diets following healthy dietary guidelines on weight and cardiometabolic health: a randomized, crossover trial. Nature Medicine. 2025;31(10):3297–3308. link
2. Hamano S, Sawada M, Aihara M, et al. Ultra-processed foods cause weight gain and increased energy intake associated with reduced chewing frequency: a randomized, open-label, crossover study. Diabetes, Obesity and Metabolism. 2024;26(11):5431–5443. link.
3. Lane MM, Gamage E, Du S, et al. Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses. BMJ. 2024;384:e077310. link.