First of all, we must find out the reason for getting fat. Why do people get fat? Just one fundamental reason: input > consumption! When you eat too much, your body doesn't need so much nutrition, so it turns into fat and accumulates. If you want to keep yourself from getting fat, you must keep it: daily intake of calories = body consumption of calories. If you want to lose weight, you must do it: calories consumed every day > calories consumed. This is the principle of losing weight.