How to stop my stomach grumbling?

Recently my stomach has started grumbling in class, and it's really embarrassing. I think its because i have an empty stomach because right after I eat something it stops. I think its because I have a really fast metabolism and I'm always hungry and my stomach rumbles just a few hours after I've eaten( especially in the morning). It's really annoying and I can't keep on having snacks every day, so do you have any other tips or advice( food to avoid, food that fills me up for a long time etc)? thanks xxx