Why the calorie is the world’s most misleading measure. "The calorie as a scientific measurement is not in dispute. But calculating the exact calorific content of food is far harder than the confidently precise numbers displayed on food packets suggest. Two items of food with identical calorific values may be digested in very different ways. Each body processes calories differently. Even for a single individual, the time of day that you eat matters." In The Economist's 1843 magazine, Peter Wilson says why it's time for us to leave the calorie behind.