There’s absolutely no easy way to bring up someone’s weight in conversation without risking them getting offended or put-off. They want to say something (either because they’re gossipy, or they’re genuinely concerned), but it’s too taboo most of the time.
The only time I see it attempted is by people casually bringing up dieting or something in conversation and trying to try to segue that into heavy hinting and get you to spill it. It also happens with my Japanese coworkers, but only because they aren’t too familiar with our customs (and that being overweight is a serious no-no for them).
Most of the folks at my office don’t care. They’re all much older than I am and they know to mind their own business. My family I’m sure talks about it, but we’re not a very confrontational group. We like to talk about each other in private—my boyfriend gets a lot of hinting from my parents when I’m not around.
That’s about the extent of it so far, but I’m sure I’ll run into more the bigger I get. It’s going to be less of “oh, he’s just put on a little weight…” and more of “okay, he has to be doing this on purpose now.”