i eat my roommate's food sometimes. i know it's bad but she has better food than me, and she doesn't even notice anyway, since i usually only take a couple things out of a big package [handful of chips, a couple cookies...]
How about instead of stealing it, ASK! Most of the time if it's a large package, a good roommate will share anyway. stealing their food is like stealing their money. Either buy your own or get permission. =/
This makes you an asshat. Food is freaking expensive, and clearly you've never had a roommate who steals just a "little bit." A little bit turns into a whole lot of annoyance. Just buy your own shit or think about proposing a communal food fund.
I've never really lived with anyone that I didn't share food with. What if you guys grocery shopped together and shared each others food? Then you can get good food and since you split the cost it saves some money.
Someone used to do this to me, it meant they had food left at the end of the week, but I didn't so I had no choice but not to eat some days. A thief is a thief, and stealing from a housemate is so low.