Well my advice is since you love them to just accept what they look like and love them for who they are and not care what they look like
Chubbiness is something that can be exercised away. As for looking 'old'? How about an updated wardrobe or new hairstyle? I don't know how many wrinkles he has or if his hair is graying, but balding, he can shave his head. With loving support you can help him into better looks.
dont consider it shallow you nust know what u want. would be wrong to lead him on
I believe you love this person but I also think you may use your feelings about their appearance as a reason to walk away from them if you don't deal with them.
If you don`t already, start doing some sport/activity. It is possible he/she will join later.