You aren't your usual self. Part of who you used to be is missing. People are terrible with change, it takes time for the image to adjust to the new normal. I imagine they liked you just the way you were, that's all they knew. They weren't the type to try and change or fix you. Now that you have let them in on your plan, they might feel they have permission to give this type of advice.

Stand your ground and claim your space. People defend what they know, if they percieve you are being down or hard on yourself, it will freak them out, they see the huge change, think you look great and wonder why you can't see it, and are still striving to look better. All those warning signs crop up in their heads. Ontop of a warped perception of what a healthy weight looks like, there is the terrifying anorexia campaign.

You need to address it head on. Your opinions deserve to be heard "I am dissappointed in your lack of support" " I am offended that you would label me so flippantly with a very serious disorder"

Talk about how happy you are with your new body every chance you get, how reasonable your goals are and be careful with any self depriciating talk. Once you do, if they are good friends, they will respect your decision and come back around to a supportive role, and they will rethink how welcome their reflex opinions are.

I have close people who have told me my whole life that I am not fat, and that I should not change. I was 5'8 and 190 lbs, clearly overweight. I ballooned up to 215 and people got slightly quieter with their happy opinions. However, now that I talk about a goal weight they can not fathom me any less then 160. I have massive bones, apparently, and it simply won't be possible. I will look emaciated and sick. I will loose all of my curves and look like a boy. I take mean jabs at myself and my fatty status because I think it's important to remind myself of the truth, and funny how much people scramble to hide that truth, then I just keep doing what I am doing.