My wife comes from a large family. Her parents and siblings both have a hard time with weight issues. Her mother, father and sister have all been up to about 300-350 pounds before.
My wife was about 120 pounds when we started dating, which was pretty skinny. Eventually she got all the way to 180 pounds after we had been married for awhile. It never made me feel mad or cheated and I didn't discuss her weight with her because she was very self conscious about that subject.
After awhile she decided to do something about it and started working out regularly. She's dropped 45 pounds and now she's an excercise fanatic. She works out doing high impact aerobics at the local gym 6 times a week and on top of that she lifts weights 3 times a week. She's still self conscious about her weight and I have to tell her at least 5 times a day that she looks beautiful and doesn't need to lose any more weight. She's still not satisfied with her weight even though she has a body like Beyonce from Destinies Child. But I like it.
I hope she can't get any skinnier.