An Arizona State University team built a mathematical model called DAMM, for digestion, absorption, and microbial metabolism, that adds the gut microbiome into the calorie equation and finds real differences between high fiber and Western diets.
The calorie number printed on a food label is built from three numbers: fat, carbohydrate, and protein. That arithmetic treats the digestive tract like a simple pipe, as if everything above the small intestine gets fully absorbed. A new mathematical model from Arizona State University adds the missing partner into the calculation: the trillions of microbes that live in the colon, the large intestine, and break down what human enzymes alone cannot.
The model, called DAMM for digestion, absorption, and microbial metabolism, runs food through the digestive system and estimates three separate outcomes: what the human body absorbs, what reaches the colon, and how the gut microbiome transforms the rest into substances that are either absorbed or eliminated. Standard calorie math, which traces back to the late 1800s and the chemist Wilbur Atwater, skips that last step almost entirely. DAMM puts the microbiome back into the equation, and the result is not just a different number on the label. It is a different model of digestion itself.
The work comes out of Arizona State University's Biodesign Center for Health Through Microbiomes, led by Professor Rosa Krajmalnik-Brown, with graduate research assistant Taylor Davis named on the team. In published evaluations, the DAMM model outperformed traditional Atwater-style calorie calculations and surfaced meaningful differences in absorbed calories between a high-fiber diet and a typical Western diet, the kind of gap that the old math flattens into a single number.
The mechanism is what makes the model more than a refinement. Most of the body's calorie extraction happens in the small intestine, but fiber, resistant starches, and other compounds the human gut cannot fully digest pass into the colon, where bacteria ferment them into short-chain fatty acids and other byproducts the body can absorb for energy. Some of those byproducts are absorbed and contribute calories. The rest leave the body. The size of that microbial contribution is not trivial, and it varies with the diet. A bowl of oats and a bowl of white bread can carry similar label calories and very different outcomes once the microbiome is part of the accounting.
That is the practical hook. The model is not a personal-diet prescription, and it is not a clinical tool yet. It is, in the researchers' framing, a way to make microbial metabolism legible inside the calorie conversation that already drives food labeling, weight-loss programs, and a sizable share of public-health guidance. The stated applications are better understanding of obesity, diabetes, and metabolic disorders, and eventually more personalized nutrition plans. None of that arrives by swapping the number on a cereal box. It arrives by changing the mental model that the number is supposed to represent.
The honest limitation is that DAMM is a research model, drawing on published data about human digestion and microbial fermentation rather than running inside a clinic. Its accuracy depends on the quality of the inputs it draws from, and personalization, the version of this story that would tell one reader to eat more beans and another to eat fewer, is still on the research side of the line. The critique the model makes of current food labeling is real: labels oversimplify a process that is partly microbial. The framework they sit inside, the idea that calories are a useful unit at all, is not what DAMM challenges. It is what DAMM refines.
What to watch next is whether the team can move from published data inputs to measurements of real meals in real people, and whether the gap DAMM finds between high-fiber and Western diets shows up at the scale of a clinical trial. That is the version of the story that would put "feed your microbes" on the same shelf as "count your calories," and it is not here yet.