My boyfriend just told me he has a gaining fetish

I (24F) have been dating my (26M) boyfriend for about 2 years now. During our relationship he has occasionally mentioned that he's not really interested in being super fit and is just happy with how his body is naturally. Of course, I've always thought he was attractive and love him no matter what he looks like.

But recently we have had talks about moving in together and getting more "serious" with our relationship. The other night he sat me down and started breaking down. He was apologizing for not talking to me about his fetish sooner into our relationship but he said he wanted to "come clean" about it. He's 6 foot and weighs somewhere in the 170s. He mentioned that if it was alright with me, that he would like to gain weight intentionally.

To be honest, I'm concerned about the whole thing and I worry about his health. I'm not bothered by the idea of some weight gain as that's natural as people age, but this is different. He mentioned that he would slowly want to gain weight overtime and stay around 225 pounds. I don't really care much about occasionally indulging him in his fetish during sex. he mentioned wanting to be fed and having me rub his body during sex.

What should I do about this? I really appreciate him for opening up about this and want to compromise. I know saying I'm okay with him gaining weight versus him actually putting on weight are two different things. Has anyone experienced something like this before?