Almost every packaged food today features calorie counts in its label. Most of these counts are inaccurate because they are based on a system of averages that ignores the complexity of digestion.
Recent research reveals that how many calories we extract from food depends on which species we eat, how we prepare our food, which bacteria are in our gut and how much energy we use to digest different foods.
Current calorie counts do not consider any of these factors. Digestion is so intricate that even if we try to improve calorie counts, we will likely never make them perfectly accurate.
At one particularly strange moment in my career, I found myself picking through giant conical piles of dung produced by emus—those goofy Australian kin to the ostrich. I was trying to figure out how often seeds pass all the way through the emu digestive system intact enough to germinate. My colleagues and I planted thousands of collected seeds and waited. Eventually, little jungles grew.
Clearly, the plants that emus eat have evolved seeds that can survive digestion relatively unscathed. Whereas the birds want to get as many calories from fruits as possible—including from the seeds—the plants are invested in protecting their progeny. Although it did not occur to me at the time, I later realized that humans, too, engage in a kind of tug-of-war with the food we eat, a battle in which we are measuring the spoils—calories—all wrong.
This article was originally published with the title Everything You Know about Calories is Wrong.