Hi, 

 Your body has a natural way of keeping its shape. It's not really possible to eat so much that you'll explode in the literal sense. If you eat way too much, your body will just reject the food and cause you to vomit. Your body only has a certain capacity for food intake, and if you greatly exceed that you'll start rejecting food. However, this is not likely to happen since your body will give you a signal that you're full so you lose your appetite. 

I'm not sure what you mean your belly shirnks. You can get smaller and lose some weight off your mid-section. However, losing weight won't prohibit you from eating. Even in extreme cases of weight loss like those associated with eating disordesr, your body will stay take in food, but just at a smaller quantity. Since your body needs food to maintain basic functions -like breathing and your heart beating- you always have to be able to take in and process food.