The food we eat is our energy. When we eat food, we need to digest it and the eaten food, once digested, serves as our energy that we use up for daily needs.(maybe wants like the gym or something) If we eat too much food, it will be stored and we will become overweight over time. If we don't eat enough, we will lose weight because we're not getting enough energy in our bodies, so our bodies cannot get enough energy from the food eaten, so it looks elsewhere for stored energy(our fat and muscle cells Hope this helped:)