A "friend" has changed for popularity; how do i best suggest he be true to himself again?

Last year I liked this really sweet, shy guy Lukas. He was always into soccer and over the summer he got really muscular from it. So now due to this change in looks he acts really vain, pervy, and otherwise a jerk. I go to a different school now but i saw him recently and was disgusted by his outward change in behavior! He's totally different! I really want to help him, but idk what's best for him and I don't know how to help him even if it is best for me to try to get him to stop acting for popularity(I've known him for long enough to know that he is indeed acting to gain friends and isn't really like this). I also owe him because he was kind to me and because of that also made me realize that I was being bigoted against him for supposedly being a bigot(stupid, I know. He's Austrian, and I had a thing against anyone German/Austrian/Japanese...)so I can't just let this go. My friends who still go to school with him don't put up with him so when they yell at him for being pervy he gets upset since he has a crush on one of them. She liked him back last year but hates him now because he treats her like a piece of meat if you get what I mean. He's still really sensitive and I think he's just acting like this to get popular, so I think there could still be hope. I don't want to make things worse! What should I do? I need to get him to act like himself again for his sake, the sake of his family, the sake of my friends and for my own sanity. btw, sorry this is so long-I ramble:)