Is it rude to ask my fat friends to be bridesmaids when I'm so much more fit and attractive?

I don't want to hurt their feelings by asking them to be in my wedding because most of them are really big and can't fit into anything smaller than an 18, and I wear a size 4. Most of them have never had boyfriends either, so that's a double wammy to have their very attractive friend get married. Should I pick people I'm less close to but are more thin and less likely to eat their way into a jealous coma? Or should I just let them be in the wedding and hope they get over their bitter feelings soon?