How do i tell my girlfriend she is getting heavy without being an A-hole or ruining her self esteem?

I really love my girlfriend, but recently i have started feeling like she is not taking care of herself, eating alot and hardly excercising at all, and putting on weight everywhere.

When i met her she was really taking good care of her body, but as we are going more and more steady i feel her interest in taking care of herself is waining at the same speed.

I feel like a shallow asshole, but she is approaching the point where im getting less attracted by her, and I want to be sexually attracted to my girlfriend.

I know no girl looks like a supermodel, but atleast eating moderately and some excercise feels like it would not hurt. I want to help and inspire her to take better care of herself, how would you guys do that (and please no BS about giving her bad self esteem, i love my girl and i want her to be happy).

And ladies, ideally, how would you want your BF to react?