How do I get my roommates son to stop stealing my food?

I am a roommate in a household with a man and his teenage son. They own the house and I pay rent. I have lived here for 3 years and for the most part everything has been fine but I have had this problem since I moved in. We share the kitchen and I have 2 cupboard shelves for my pantry items. There have been countless times where I would go into the closet where my food is and I can tell that things have been taken. I would even count things before I left and when I come back there will be some gone. The food that is being stolen is sweets like cookies and pop-tarts ect. The son is 16 years old. He does not have a weight problem. His father buys enough food for both of them but that's not always the case with sweets. I have been thinking about what I can do about this without having to confront him or his dad. Its frustrating because I don't want to rat him out but I also cant afford to let this continue. I don't want to have to stop buying the food I want. I also don't want to have to resort to keeping food items in my bedroom. Maybe there are special containers or alarms that might scare him into not trying to steal again. I don't know. Any advice would be helpful.