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Randomized trial · measured the question itself

1-week trial in 9 Japanese men: more weight gained on ultra-processed meals

Hamano and colleagues · Diabetes, obesity & metabolism · 2024

Original title: Ultra-processed foods cause weight gain and increased energy intake associated with reduced chewing frequency: A randomized, open-label, crossover study.

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What the study found

Points to harm

On the ultra-processed diet, men gained 1.1 kg more weight (95% confidence interval 0.2 to 2.0) and ate 813.5 kcal more per day (342.4 to 1284.7). They chewed less per calorie.

The study at a glance

Type of study
Randomized trial
Who or what was studied
9 people · 9 overweight or obese Japanese men without other medical conditions
What was tested
Ultra-processed vs non-ultra-processed meals for 1 week each, with a 2-week break, meals matched for calories and nutrients
What it measured
The question itself: death, heart disease, diabetes and cancer
How long
1 week
Who has a stake
No disclosure in PubMed
No disclosure in PubMed; funded by a Japanese government ministry.
Journal
Diabetes, obesity & metabolism, 2024
Source
PubMed record 39267249. This page is based on the abstract only.

How much this study counts

  • ✓Randomized: people were put into groups by chance, so the groups start out alike.
  • –Small: 9 people. Small trials can miss real effects or find chance ones.
  • –Short: 1 week. Longer-term effects are unknown.
  • ✓Measured the question itself: death, heart disease, diabetes and cancer.
  • •The PubMed record has no conflict-of-interest statement.
  • •Summarized from the PubMed abstract only. The full paper may hold details the abstract leaves out.

✓ Strength– Limit• Note

These points come from fixed rules about the type of study, its size and length, what it measured, and who has a stake. Every study on Digestery gets the same rules.

Where this study sits

Each dot is one on-topic paper on this question. Steps near the top answer the question more directly.

↑ Stronger evidence

  1. Trials in people: death and chronic disease

    2

    1 no difference, 1 harm

    ↑ This study is the ringed dot

  2. Trials in people: other measures

    3

    1 mixed, 1 no direction, 1 harm

  3. Trials in people: lab tests or safety

    1

    1 mixed

  4. Population studies

    17

    1 mixed, 16 harm

  5. Blood levels and genes

    0

    None among the papers we read.

↓ Weaker evidence

  • Points to benefit
  • Mixed
  • No difference
  • No direction
  • Points to harm

How it fits with the other research

The short answer to “Are ultra-processed foods bad for your health?”

Linked to worse health; cause not proven.

Confidence: low. Based on 38 on-topic papers.

Read the full answer

Few other papers sit on the same step, so there is little to compare it with.

Other papers on the same step

See all 38 studies on this question

How this page was made

Label

First read of the abstract
Claude Sonnet
Independent second read
Claude Haiku
Differences settled
The reviewer corrected 1 field after reading the abstract. Claude Opus 5.5.
Headline
Claude Sonnet, from the checked study record. A script checked its numbers and wording.
Numbers
Checked against the abstract by a script
“How much this study counts”
Fixed rules, the same for every study
Source check by a person
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