I am fairly sure (though have no proof) that eating less does indeed shrink your stomach.
But I wish to ask: to what end? It's not like a smaller stomach will cause you to lose weight, if that's where you're goin'.
The stomach is an extremely flexible organ and will simply expand as needed. Think about filling a nylon mesh bag. Empty it and crush it up, it will re-open quite small, but that doesn't mean you'll have any trouble stuffing it full of books. It's not like the resilience of the mesh is strong enough to resist putting a book in it.