how about working out outside of the home? if you cant afford to join a gym or anything, go walk or jog. of course he'll see you coming and going, but there has to be a point that you put yourself ahead of whatever he might think and/or say. if you really want to do this, you are doing it for YOU...dont worry about him. besides, if you lose the weight, he cant say anything about it anymore!
Go for it! show him up!!! I challenge you!