Fuck me I got to the age of 33 with people thinking it was fine to call me a 'skinny bitch' in public because apparently that was a compliment?!?
OP, when people mention your loss I'm sure it'll mostly be in a congratulatory manner.
When people say, "We could all look like you if we stopped eating cake", just shrug because it's neither here nor there to you what they eat is it?
And when people tell you to stop losing weight, their concern can often be misguided but not necessarily fake.
I was saying on here the other week that I picked up a magazine with a photo of a woman who looked 'chubby' to me.
But upon reading the story, it turned out she'd lost something like 10 stone.
Now to me (having never laid eyes on her before) she did look chubby...but to those who knew her as 10 stone heavier...she must have looked decidedly thin.
So sometimes it's more about how people have always been used to seeing you, rather than how thin you actually are...that makes them 'concerned'.
As long as you know you're losing in a healthy way and are happy, just smile and nod.