That kind of sounds like the typical "I can change him"-myth.

And by saying that you are not superficial but you want him to change for you "because you deserve to feel attractive to him as he feels attractive to you" sounds extremely superficial. So he's nice and all but he's just not enough for you because he's bigger. Well though titties. Maybe you're not malicious (and I don't think you are) but it sounds very manipulative.

Did you ask him if he's happy with the way he feels and/or looks? Why should he change for you (or as a matter of fact for anyone) if he's happy with the lifestyle he has?

If you truly believe he would benefit from your lifestyle maybe try talking to him and seeing he's up for your advice rather then asking internet strangers how to change a person just because the way they look (because at the end those are your primary motives). If he can't change it or is happy the way he is then you can only accept that or move on.