Not to flog a dead horse, but there is a general point I'd like to make. The one thing that would have changed the whole situation was if the woman in question had expressed a desire herself to lose weight or eat more healthily. But assuming that someone wants to be more like you in some way when they haven't actually said so does easily come over as patronizing.

On the other hand, I think many of us are guilty of this. We're only human, and the more convinced we are that a certain behavior or a certain habit is not just a good thing, but practically life-changing, the more likely we are to prescribe it whether someone asks or not. And the more likely we are of being thought of as annoying zealots. Biking, healthy eating, crossfit, religion, political views - we all have these people in our Facebook feeds. We just don't notice them as much when they're talking about things we agree on.