Dude at my old job started making a lil money and ate Chinese at his desk basically every day for 3 months. He was obviously getting bigger, man b00bs and such. I wasn't that cool with him so I never mentioned it. One day I was talking to this girl and dude passed by and she made a face and said 'he's gained weight'. After that I figured I'd bring it up to him on the low. I even asked if he wanted to hit the gym sometime. Son got offended and had the nerve to say it only looks like that because his shirt is big, there was another dude in earshot and he frantically hopped on dudes side. Smh. About a week later, he came to me and said that he would like to hit the gym sometime. Everyone isn't receptive to criticism and it may be a big splash initially, but after it settles, depending on their maturity, they may understand that it's constructive.
Criticism like that I take very well. If people tell me I'm looking pudgy or frail, I thank them and adjust my diet and workout routine.