either my father's a jerk, or I'm oversensitive

Don't let him sabotage you. Murder him first!

but wait till after Christmas...he might get you a nice gift

then....OFF WITH HIS HEAD!

Don't eat - if you eat you let your dad win. Plus you will just be more mad at yourself - I have been there, done that.
Show him!!!
That's the mind set I have taken lately with alot of things in my life. I am tired of people winning, time for me to take control of me.
And ps - I would be upset too. I really feel those comments come from their insecurities.

I told my father today how much weight I've lost. (19 pounds in 9 weeks) and was for some reason expecting some sort of congratulations or way to go. He smirked at me and said "you know Christmas is coming, right?" I said that it comes every year, for fat and skinny people and walked out.
I know that I'm probably overreacting but I'm really upset. To me he was saying that I'm just going to gain it back so why bother. So of course now I want to eat, because that's what I do when I'm upset.

Don't indulge in food. You came here to change that and we aim to assist! Remember how eating won't make you feel better but will actually make you feel worse after you indulge.. not THAT you do it but WHY you do it. Don't let his insensitivity bring you down.

This is your dad. I would expect that he means well. While the manner in which he chose his coment was wrong, maybe he meant it as a reminder that the toughest time of year is coming and he hopes you will be able to overcome those tough situations. Eitehr way, communicate with him that you were hoping for some encouragement and feel rather let down by his response. I'm sure he didn't mean to be mean or discouraging.

HOWEVER if he did mean it that way, then I would go as I would were it my step mother. USE THAT COMMENT TO FUEL YOUR SUCCESS. Other family members are bound to see your progress by the holidays and some are bound to be encouraging. Use this to show him you are stronger and his downplaying your effort is only going to fuel your desire to be sucessful SURING the hardest part of the year. Then when you succeed, maybe he will remember some humane aspect within him and become suportive.

and incidentally, my doctor was the one who was title King of rude and earned himself the nickname of Dr. Demented when I finally decided it was time for me to change. It was wrong but it has worked for me. I let his rudeness and mean comments of how fat I was and how I was setting myself to die of a heart attack get me to a point of "I will show you!" When I left his office ALL I WANTED TO DO was drive through the nearest McD's and order EVRYTHING and eat it. Seriously. I sat in the parking lot for 20 minutes in hysterics and tears an belittled to nothing. The alter ego I now refer to as the inner goddess became very prominant to me that day. She Flew out of no where in my head on a which's broom cackling like a lunatic shouting "Show that bass-TURD! You show him you CAN lose weight and you DON'T need his stupid HCG diet! You just show him! *more evil cackling*

I took me 4 days to figure out my plan of attack. I've lost 47lbs since May. BTW Dr. Demented earned the title of former doctor to me and has never been given the chance to see my success but I amde CERTAIN that before I changed docs his office got my bloodwork from August showing a HUGE change in stats INCLUDING my glucose being under control by diet ALONE.

There is no shortage of dumb comments from parents.
The first time I hit a ball over the fence my father said "it's about time. you should have done that years ago."
When I was in college he referred to my degree as "whatever the hell you're studying."
If he were alive, I suspect he would say some similar to what your father said (He died a painful death from cancer in 1998).
The best we can do ignore the stupid crap and try not to internalize it. Believe me, I know how hard that is. I also try hard not to repeat the same mistakes with my own children. So far so good.

This is not an easy journey. And you've got this. Good for you!