Gut bacteria change how many calories your body actually absorbs from food
A new Arizona State model shows gut microbes shape calorie absorption. High-fiber eaters absorbed about 116 fewer calories daily without feeling hungrier.
Summary
Gut microbes and calorie absorption are the focus of a new Arizona State University study. Researchers built a mathematical model called DAMM (digestion, absorption and microbial metabolism) that tracks how food moves through the digestive tract, how much energy the body absorbs directly, and how gut bacteria process what is left over. The calorie numbers on food labels rely on century-old Atwater values, which ignore the microbial role. In a controlled study, people eating a high-fiber diet absorbed about 116 fewer calories per day than people eating a typical Western diet, and they did not report feeling hungrier. Part of the reason is that microbes ferment fiber into short-chain fatty acids, some of which enter the bloodstream and supply extra energy. The team hopes the model will improve understanding of obesity, diabetes and other metabolic disorders, and could eventually support diets tailored to individual patients. The findings were published in PLOS One.
Detailed Summary
Food labels suggest that calories are a fixed property of what we eat, but this research shows that the energy your body actually extracts depends partly on the trillions of microbes in your gut. That matters for anyone managing weight, blood sugar or long-term metabolic health, because small daily differences in absorbed energy add up over years.
Researchers at Arizona State University, working with scientists at the AdventHealth Translational Research Institute, developed a mathematical model called DAMM, short for digestion, absorption and microbial metabolism. It follows food through the digestive tract, estimates how much energy the body absorbs directly, models how gut bacteria metabolize the remainder, and predicts which products are absorbed and which are excreted. The work was published in PLOS One.
The model addresses a gap in the Atwater system, used for more than a century. Atwater values assign average calories per gram of fat, carbohydrate and protein, but they do not capture how different foods feed gut bacteria. When microbes ferment fiber and other material that escapes the upper gut, they produce short-chain fatty acids, and some of these enter the bloodstream and provide additional calories. In a controlled study, people eating a high-fiber diet absorbed about 116 fewer calories per day than those eating a typical Western diet, without feeling hungrier.
The practical message is that feeding your gut microbes properly, chiefly with fiber-rich foods, may change your net energy intake without added hunger. Over time, this approach could inform personalized nutrition for obesity, diabetes and related metabolic disorders, though the researchers describe such tailored diets as a future possibility requiring further development.
There are caveats. The 116-calorie difference comes from a specific controlled study and may not apply to everyone, since microbiome composition varies widely between individuals. DAMM is a model, not a clinical tool, and it has not been shown to improve health outcomes. Readers should consult the PLOS One paper for details on study size, diet composition and model validation before drawing firm conclusions.
Key Findings
- DAMM models digestion, absorption and microbial metabolism to estimate the energy actually absorbed from food.
- High-fiber eaters absorbed about 116 fewer calories daily than those on a typical Western diet.
- Participants on the high-fiber diet did not report feeling hungrier despite absorbing fewer calories.
- Microbes ferment fiber into short-chain fatty acids, which can enter the bloodstream and add calories.
- Century-old Atwater values ignore gut bacteria, so food label calories may not match real absorption.
Methodology
This is a university press release summarizing a modeling study with a controlled dietary comparison, published in PLOS One. The source is credible, with named researchers at Arizona State University and AdventHealth Translational Research Institute. The press summary gives limited detail on sample size and validation.
Study Limitations
The article does not report participant numbers, study duration or how well the model predicts individual results. The 116-calorie figure is an average from one controlled study, and individual microbiomes differ. Check the PLOS One paper for full methods and whether health outcomes were measured.
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