i doubt it...if your hermit were too fat to get out of its own shell, it wouldn't be able to stay in the shell in the first place.......but if you still think this is the case, here's what you can do......prepare empty shells of varying sizes.....crack your hermit shell gently (try not to hurt its soft underlying tissues)....this will force your hermit to find a new home....and hopefully he'll find one......
i've never done this before, so you'll be the first one...good luck!!