<human>: Can you summarize the given text in a few sentences?

Before, my friend used to be a genuinely good guy and was always fun to hang around. In the last year, he's lost a good amount of weight (I helped him out at the gym, taught him to count calories, etc.) and now he acts like a complete asshole, a complete 180 to what he used to be.

Earlier today, him and I were walking through campus and he saw a slightly overweight girl. Immediately, he started laughing and told me to "man the harpoons" all while this girl was within earshot of us. Other times, in our dorms, he'll walk around shirtless or lift his shirt to try and impress girls with his physique. Seriously, he can't even walk past a window without looking at himself and talking about how good he looks. Anyways, you get the idea.

He still gets along with me and we're still friends, but his behavior otherwise is really starting to piss me off. So Reddit, how do I break the news to my asshole friend?
<bot>: Friend used to be a Good Guy Greg, lost 40 lbs, now is a complete asshole with an inflated ego. How do I tell him I liked him better when he was fat.