How Do We Know What Calories Are in Food?

Calory counting goes back a hundred or so years, but we haven't really moved on. We've this idea that it's a very precise measure that is the best way of looking at food. And you can't measure how much you put in your body, because it's er. It's really tricky to do. The second thing is that all callories are supposed to be equal. This is the basis of low calory diets and low calory labels. So there's tons of reasons why really we should down grade the calory to a historical artifact. But most of us have got this balance wrong.