> Anyone who's taking grade 10 physics can tell you exactly why the difference between calorie input and calorie output equals your change in weight. This is o

> Anyone who's taking grade 10 physics can tell you exactly why the difference between calorie input and calorie output equals your change in weight. This is one of those places where you can be entirely correct but entirely unhelpful. The problem is that calorie output is both a) non-constant (even your base metabolic rate changes over the course of your life, much less any lifestyle changes) and b) influenced by environment and physical condition (your calorie burn will change in response to environmental pressures, including caloric restriction and changing body fat content).