Food and Behaviour Research

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Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake

Hall KD, Ayuketah A, Brychta R, Cai H, Cassimatis T, Chen KY, Chung ST, Costa E, Courville A, Darcey V, Fletcher LA, Forde CG, Gharib AM, Guo J, Howard R, Joseph PV, McGehee S, Ouwerkerk R, Raisinger K, Rozga I, Stagliano M, Walter M, Walter PJ, Yang S, Zhou M (2019) Cell Metab. 30(1) 67-77.e3. doi: 10.1016/j.cmet.2019.05.008. Epub 2019 May 16. 

Web URL: Read this and related articles via PubMed here. Free full text of this article is available online



  • 20 inpatient adults received ultra-processed and unprocessed diets for 14 days each
  • Diets were matched for presented calories, sugar, fat, fiber, and macronutrients
  • Ad libitum intake was ∼500 kcal/day more on the ultra-processed versus unprocessed diet
  • Body weight changes were highly correlated with diet differences in energy intake


We investigated whether ultra-processed foods affect energy intake in 20 weight-stable adults, aged (mean ± SE) 31.2 ± 1.6 years and BMI = 27 ± 1.5 kg/m2. Subjects were admitted to the NIH Clinical Center and randomized to receive either ultra-processed or unprocessed diets for 2 weeks immediately followed by the alternate diet for 2 weeks.

Meals were designed to be matched for presented calories, energy density, macronutrients, sugar, sodium, and fiber. Subjects were instructed to consume as much or as little as desired. Energy intake was greater during the ultra-processed diet (508 ± 106 kcal/day; p = 0.0001), with increased consumption of carbohydrate (280 ± 54 kcal/day; p < 0.0001) and fat (230 ± 53 kcal/day; p = 0.0004), but not protein (−2 ± 12 kcal/day; p = 0.85). Weight changes were highly correlated with energy intake (r = 0.8, p < 0.0001), with participants gaining 0.9 ± 0.3 kg (p = 0.009) during the ultra-processed diet and losing 0.9 ± 0.3 kg (p = 0.007) during the unprocessed diet.

Limiting consumption of ultra-processed foods may be an effective strategy for obesity prevention and treatment.


This study - a carefully conducted randomised controlled trial - provides the first definitive evidence in humans that eating a diet high in 'ultra-processed food' actually causes increased appetite and food intake, and therefore weight gain.

Evidence from experimental or pre-clinical studies has already shown that ultra-processed foods can override normal appetite regulation and satiety signals, e.g:
There is also abundant evidence from population studies that diets rich in these foods are both linked with, and predict, obesity and related physical and some mental health conditions, such as depression:

What has been lacking, until now, is good controlled clinical trial evidence that ultra-processing itself can confer harmful properties on foods or diets - leading to effects that cannot be explained away by the calories or nutrients they contain.

See the associated news articles:

And for more information on the effects of ultra-processed foods on mental as well as physical health, please see: