The Study
Quantifying the varying harvest of fermentation products from the human gut microbiota
This study is like building a detailed computer model of how gut bacteria break down food, using lab experiments and known facts about digestion. It helps us guess how much energy we get from gut bacteria on different diets, but it doesn’t prove it happens exactly that way in real people.
Analysis score
Maximum 0 for a computational/algorithm study.
Where the score came from
Your gut bacteria eat the fiber you can't digest and turn it into tiny amounts of energy that your body can absorb. What you eat matters way more than which bacteria you have.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 50 / 100
Quality score
Based on clinical experience or non-systematic literature reviews. The lowest level of evidence as they are most susceptible to bias and personal perspective.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This energy boost is small for humans but may still support gut health and metabolism, especially on high-fiber diets.
- 2People on Western diets get 2%–5% of their energy from gut bacteria; those on high-fiber diets get up to 10%, sometimes 12.1%.
- 3Mice get over 21%.
- 4Over 90% of the fiber eaten by bacteria turns into useful energy molecules; less than 2% is wasted in poop.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Cell
Year
2025
Authors
M. Arnoldini, Richa Sharma, Claudia Moresi, Grifin Chure, Julien Chabbey, E. Slack, Jonas Cremer
Related Content
Claims (5)
The gut bacteria in people eating lots of fiber can provide up to 12% of their daily energy, while those on a typical Western diet get only 2%–5% from their gut bugs — so what you eat changes how much energy you get from your microbiome.
What you eat—especially fiber and complex carbs—mostly decides how much gut fermentation happens, and eating more of these carbs can boost fermentation by up to five times compared to a standard Western diet. The types of gut bacteria you have don’t really change the overall amount.
Most of the stuff your gut bacteria eat turns into helpful chemicals like butyrate, and your body soaks up almost all of it—very little ends up in poop.
Your gut bacteria don’t change how much waste they produce overall, but they do change what kinds of waste chemicals—like butyrate and lactate—are made, and this mix is different for everyone depending on their unique gut bug lineup.
People can't break down tough plant fiber like cows or rabbits can, so we get almost no energy from it — their stomachs are built for that job, but ours aren't.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.