Well that makes it difficult when you can't grocery shop and the others are buying crap. The only thing you can do in that situation is talk to them and see if they buy you some things (lean protein, fruits, veggies) and use portion control. No matter what you eat, if you use portion control you can still lose weight. There's a saying I love. If you really want to do something, you will find a way, If you don't, you will find an excuse. Find a way! You can do it!