Your Gut Bacteria May Have a Say in How Many Calories You Absorb

Something Doesn’t Add Up: Calories in, calories out is the golden rule of managing weight. This simple equation says you lose weight by burning more calories than you eat. But a new study suggests your calorie tracking app is probably overlooking something — microbes in the gut may also influence how many calories you actually absorb from food.

The Study: Researchers at Arizona State University created what’s basically a calculator for digestion. You plug in what someone typically eats, and it estimates how many calories the body absorbs on its own and how many extra come from gut bacteria breaking down fiber. An earlier study tested this by having 17 healthy adults eat a high-fiber, less processed diet and a typical Western one (smaller particle size and more processed food) for about three weeks each. On the Western diet, people absorbed about 116 more calories a day, and the high-fiber diet didn’t leave them feeling hungrier.

The Takeaway: Calorie counts on labels are estimates. Also, filling up on fiber-rich, less processed foods could mean absorbing fewer calories without feeling hungrier.

Keep in Mind: The model is still just a research tool. Scientists need to test it on more people and eating patterns before doctors can use it to tailor diets.