Hi Melody,
I have to say, from your avatar, you are a beautiful woman!! I think these people are definitely jealous! It's their insecurities coming out.
I am like you, I can't think of a come-back at the time, but later on, after thinking about it, I can think of several things that I wish I would have said to them.
It's a shame when others can't be "just" happy for us for improving ourselves and for just being us, whether we are fat, skinny, tall, or short!!
Good Luck to You!!
Take care,
Linda