You can't force them. The best you can do is become a living example of how sexy, vibrant, alive and healthy a human can become and hopefully, this will inspire them.
As for thinking they need to eat meat for big manly muscles, get them the "Raw Vegan Muscle" DVD set. Tell him if he wants to not lose any more hair, not have any more prostate problems or "performance" issues, maybe he should give it a try.
If you have been "reborn" and see the light, but they don't, and you see yourselves drifting apart, you need to allow life to take you where you need to go. This is scary for some because many women see men as their form of security, but this is an illusion. Do you want to live as an unhappy slave for the rest of your life? And it might not turn out bad- if the other person really wants to do the right thing and become a better person, then they might be inspired by your strength and dedication. They might also be afraid of losing you because now you look sexy again and this is when they realize how much you actually contribute to the relationship, and how lost they would be without you. But it's not about who's right or wrong, it's about following your own truth and not being afraid.