Misadventure it's good to hear that you wouldn't tell anyone that they had gained weight because THAT would be rude. Of course a sensible discussion is fine. If it was my partner or adult child who was smoking or drinking too.much. I would first ascertain and tackle the cause rather than the behaviour because you want to help them, not give your uninformed opinion and leave them to it.
Notanan2 if you are distracted with life events, the last thing you need is someone telling you that you have put on weight. Society is changing, full stop. Yes people are trying to live their life in a positive way, would you rather them live their life full of angst and negatively, so you can continue to beat them with the skinny stick.