Adopted children and food obsession?

Could you try simply explaining the concept of FOOD IS FUEL...talk about in the context of a car etc...There is XYZ amount of calories and food types your body needs each day. That is all you should eat....period. Kids with emotional issues sometimes cannot tell when they feel full or hungry. You need to explain to them that the stomach is like a balloon. It stretches and shrinks....so feeling hungry isn't always a reason to eat. Neither is feeling sad, or bored...etc...This helped my dd normalize her food issues (starving herself). She was anorexic at age 3.