Calorie counts on food labels assume a fixed energy yield per gram of protein, fat, and carbohydrate, but the body's actual absorption depends on more than food composition. Arizona State University researchers have developed a mathematical model called DAMM (digestion, absorption, and microbial metabolism) that accounts for the role of gut bacteria in processing food. The model tracks food through the digestive tract, estimates energy absorbed directly, and calculates how microbes transform leftover material into compounds like short-chain fatty acids that can enter the bloodstream.
In a controlled diet study, healthy adults eating a high-fiber, resistant-starch-rich diet absorbed about 116 fewer calories per day than those on a typical Western diet with more processed foods. The fiber-rich group did not report feeling hungrier, suggesting that the energy difference came from changes in digestion and microbial activity rather than reduced intake. The findings indicate that food labels may not reflect the energy a person actually obtains, especially for diets differing in processing and fiber content.
The DAMM model also estimates that gut bacteria can supply roughly 140 calories a day through their metabolic activity. The researchers hope this approach will improve understanding of obesity, diabetes, and other metabolic disorders, and eventually help clinicians design personalized diets. According to the study, digestion is a collaboration between human cells and trillions of gut microbes, and the model provides a quantitative way to measure that partnership.