Picture someone who has to break up the ice covering their driveway after a winter storm. They buy a bag of salt that then must be distributed across the ice. What would happen if they concentrated all of their salt in one area of the driveway? While the ice in that one section may be thoroughly broken up, there would of course not be any salt left for the remainder of it.
In Ayurvedic tradition, a person's health works in a similar way. Like the bag of salt, the human body has a finite amount of resources to maintain its various systems (the immune system, the nervous system, etc.). But, when we eat too much food, we burden the digestive system which then diverts resources away from the other ones. Then, when all of the resources are devoted to the digestive system functioning, not only is there a likelihood of stomach disorders, but there's a likelihood of other systems like the immune system falling short as well.
This is why Ayurveda not only helps to treat stomach disorders, but resolving them and balancing digestion is at the very heart of how it is effective as a medical system. When you eat balanced food in appropriate amounts, you will not only resolve any stomach issues that you have but you will begin to attain greater overall health as well.