Plate Nº 72 · recorded October 13, 2026
Health & Medicine ResearchReported finding
Gut Bacteria May Add About 140 Calories a Day, ASU Model Finds
Arizona State University researchers built a model showing gut bacteria supply roughly 140 calories a day through fiber fermentation. In a clinical trial, high-fiber eaters absorbed 116 fewer daily calories than Western-diet participants.
By Elena Vasquez3 min read659 words
In brief
- High-fiber diet cut calorie absorption by 116 per day versus a Western-style diet in the controlled trial.
- Gut microbes supplied an estimated 140 calories per day through short-chain fatty acids, about 7.4% of usable energy.
- Roughly 85% of usable energy came from the upper gastrointestinal tract, 15% from the lower tract where microbes dominate.
- Findings published in the May 2026 issue of PLOS One; clinical data came from a study run with AdventHealth Translational Research Institute in Orlando.
- Authors include ASU's Rosa Krajmalnik-Brown, Bruce Rittmann, and first author Taylor Davis.
A high-fiber diet cut daily calorie absorption by 116 compared with a typical Western diet in a controlled clinical trial, according to a new model from Arizona State University that quantifies the hidden role of gut microbes in human digestion.
The model, called DAMM — short for Digestion, Absorption and Microbial Metabolism — tracks food from the mouth to the colon. It estimates how much energy the body absorbs directly and how much gut microbes contribute by fermenting what remains. Published in the May issue of PLOS One, the work folds ASU's math into a clinical study run with the AdventHealth Translational Research Institute in Orlando, Florida.
"Digestion is not just a human process — it is a collaboration between our bodies and trillions of microbes living in the gut," said Rosa Krajmalnik-Brown, director of ASU's Biodesign Center for Health Through Microbiomes. DAMM, she added, gives researchers "a powerful new way to quantify how those microbial partners contribute to human health and energy balance, and also point at the importance of properly feeding our gut microbes."
How much do gut microbes really contribute?
Roughly 15% of usable food energy comes from the lower gastrointestinal tract. The upper gut handles the other 85%.
In raw calories, that microbial share works out to about 140 calories per day from short-chain fatty acids — compounds gut bacteria produce when they ferment fiber and resistant starch that escaped earlier digestion. That figure lands around 7.4% of total usable energy, the researchers estimated.
The model also tracks methane production by methanogens, microbes that generate methane as a metabolic byproduct.
Takeaway: Gut bacteria aren't passengers. They hand the body about 140 extra calories a day.
What did the clinical study find?
The team fed DAMM data from a controlled feeding trial of healthy adults. One group ate a microbiome-enhancer diet rich in fiber and resistant starch, with less processed food and larger particle size. The other ate a Western-style plan: more processed food, smaller particles, less fiber.
Western-diet participants absorbed about 116 more calories per day than the fiber group. Both diets were designed for the study. Their bodies simply held onto more energy.
Higher-fiber eaters didn't report feeling hungrier. That's a quiet second headline.
Blood serum and fecal measurements backed the math. Fiber-eaters showed higher short-chain fatty acid levels.
Why the calorie count on the box isn't the final word
Nutrition labels lean on Atwater parameters — average calories per gram of fat, protein, and carbohydrate. Scientists have used the system for more than 100 years. It ignores what happens after food leaves the small intestine.
That blind spot costs accuracy. The Atwater approach underestimated calorie absorption in the trial. DAMM's predictions ran closer to measured values.
"What is truly unique about the DAMM model is that it quantitatively links human metabolism to the metabolism of the microorganisms in the colon in a way that matches the results from the clinical study and provides fundamental insight into how the microbial community works in partnership with the human host," said Bruce Rittmann, an ASU engineering professor and co-author.
Takeaway: A food label is a starting estimate, not a final tally.
Could this lead to personalized diets?
Someday. The team built DAMM to grow with the science.
"It's a framework designed to evolve," said first author Taylor Davis, an ASU graduate research assistant. "As we discover more on how diet, metabolism and the microbes interact, the new insights can be incorporated into the model, allowing it to grow with us as we learn."
For now, it remains a research tool. Open questions include how DAMM performs across different populations, eating patterns, and microbiome compositions. The links to obesity and diabetes still sit in the hypothesis column, awaiting larger trials.
The bottom line: the calories printed on the box rarely match the calories your body keeps. Trillions of microbes help set the gap.
via doi.org (Original)
More from Elena Vasquez
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Correspondent covering money, funding and market shifts around general science news at SciBeat.
228 articles
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