My weight is nobody else's concern so I don't ever mention it in casual conversation. Same with my food choices, my muscles, my size, my disordered eating history. We can just go down the list checking, "Not your business. Not your business. Not your business." Especially with clueless looky-loos making off-handed comments. It's not worth my time or energy to bring them up to speed, hoping that I've explained it in such a way that they will understand and approve. They don't care. That was a revolutionary notion. Most of the time they're just making conversation. They're not going to go home and lose sleep over my size or choice of ice cream toppings, so why should I?
Once in awhile I will run into someone who is genuinely interested. I'm always happy to talk food, fitness, mind/body with someone who is sincere and receptive, especially if they're asking for my help. That's not most people though. Your average relative or coworker is just making fly-by small talk and projecting their own issues.