Is it normal if i don't want my bf to loose weight?

I've been with my boyfriend for 5 months, we love eachother, we get along really well but since he told me he wanted to lose weight, I feel weird about it. When we met he was about 233 lbs and haven't changed yet and I'm kind of afraid of it.
I know that it's bad for his health to do nothing and would feel like a piece of crap to leave him for such a shallow thing, my mind thinks it's wrong and my heart too but there's another part which I do not know so well, maybe a sort of "fetish part" that doesn't want him to be thinner. I don't know how I could react if he actually will get. I already hate myself that I asked him to put on some weight, this sounds like I do not like him the way he is and I find it hurtful. He says "it's OK" and I'm not responsible of what I like despite, I feel weird, shallow, confused and worried.
How I will perceive his weight loss?
How weird my fetish-part actually is and can get?
Will it stay on the good side and not slip to the feederism side (which he finds unrespectful and so do I even if it's quite exciting)
I'm really lost and hateful about myself I do need some help. I don't know what to do.

I think it's normal that I don't want him to loose weight cause I'd like him to stay the way he was when we met.
But on the other side I don't think it is cause I should like him for his personnality, not only for his body.
I help him work out a little but I am confused by the situation and reaching for some help; what do you guys think?