Ultra-Processed Foods: 500 Extra Calories a Day
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Blog Nutrition November 14, 2026 Clinically reviewed by Dr. Tim Pepin on

Ultra-Processed Foods: The NIH Study That Found 500 Extra Calories a Day

In a controlled NIH trial, adults ate about 500 more calories a day on an ultra-processed diet than on an unprocessed one, even though the meals were matched for calories, sugar, fat and fiber.

In a 2019 NIH inpatient trial, 20 adults ate about 508 more calories a day during two weeks on an ultra-processed diet than during two weeks on an unprocessed diet. The meals offered were matched for calories, energy density, macronutrients, sugar, sodium and fiber, and participants could eat as much as they wanted.

Many studies link ultra-processed food with poorer health, but they cannot separate the food from the people who eat it. A trial at the National Institutes of Health Clinical Center controlled everything except the processing.

What the trial did

Twenty weight-stable adults, average age 31, lived at the research center for four weeks. Each person ate an ultra-processed diet for two weeks and an unprocessed diet for two weeks, in random order.

The meals presented on each diet were matched for calories, energy density, protein, carbohydrate, fat, sugar, sodium and fiber. Participants were told to eat as much or as little as they wanted.

What it found

  • People ate about 508 more calories a day on the ultra-processed diet
  • The extra calories came from carbohydrate and fat, not protein
  • Body weight rose on the ultra-processed diet and fell on the unprocessed diet, in step with how much people ate
Keep it in proportion
The trial was small and lasted two weeks per diet, in a research unit. It shows that processing changed how much people ate under those conditions. It does not show long-term effects.

What counts as ultra-processed

The term covers industrial products made mostly from refined ingredients and additives: packaged snacks, sweetened cereals, soft drinks, reconstituted meats and many ready meals. Unprocessed and minimally processed foods include vegetables, fruit, eggs, plain meat and fish, beans, plain yogurt and whole grains.

Practical swaps

  • Plain oats with fruit in place of sweetened cereal
  • Fruit and nuts in place of packaged snack bars
  • Plain yogurt with berries in place of flavored yogurt
  • Water or sparkling water in place of soft drinks
  • One more home-cooked dinner a week

Our guide to the protein and fiber breakfast template has quick options.

This article is educational and is not medical advice. Talk with a licensed clinician about your own health.

References

  1. Hall KD, Ayuketah A, Brychta R, et al. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metab. 2019;30(1):67-77.e3. Source
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Editorial disclosure: This article is for informational purposes only and does not constitute medical advice. All treatments at DirectCare AI are prescribed by US-licensed clinicians based on individual medical evaluation. Compounded medications are not FDA-approved and are not reviewed by the FDA for safety, effectiveness, or quality. Always consult a US-licensed clinician before starting or changing any therapy.

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