How do I tell my bf to lose weight and make him believe my reasons?

I love my bf just the way he is. He is so handsome to me and I wouldn’t change a thing about him, except that I know that being overweight is not healthy. This is the one and only reason why I would like to discuss with him more about nutrition and sport. He is aware about sport, and generally nutrition, but he’s set in his ways. I’ve tried a few times to mention how processed his food is, and even asked what is the perfect weight that he is aiming for, when he mentioned that he’s losing weight. He’s kind of ok with being overweight, saying he knows he’ll never be able to come back to a more or less fit shape, and the mayonnaise will probably stay on the table. So I don’t know how to convince him he can do it, it’s important for his health, without him thinking it might be a problem for me. I really find him so attractive, and my only reasons are just health related. I know little changes can go a big way, like giving up on white bread or sugar, or the mayonnaise!