Lifestyle tips

it doesnt really matter how many times you say to him that hes hot. Hes gotta think that for himself. Its not a quick thing to learn to love yourself.
But get him looking good. Like nice shirts, pants and shoes etc. Get a get a hair cut if needs one. If he starts to see he looks good he might start believing what your saying.

Its slow process and it wont happen over night.

No idea if this helps you.

One step along the way may be to back off your language a bit, from "you are..." to something more like "to me you are...." or even "I feel that....".

If you say " you are so handsome" you are putting your words in conflict with the impression he may get from a lot of the world, putting an uncomfortable cognitive dissonance in his head. When you use the subjective phrasing it may be easier for him to accept that you adore his current body.