Parents are being really bad support?

So, I live with my parents (Planning to move out soon, though, if everything goes well ), and for the most part of the day I don't see them, but when I do, they'll mock me for trying to eat healthy, and for being a vegetarian, too. They're both "crash" dieters, going from overweight to normal (and vice versa) in short periods of time, via "healthy" (as they call it) methods. These "healthy" methods involve rarely eating, and when they do eat, it's chips, or they'll get calories by drinking cheap beer. Once they lose weight, they'll go back to their old ways, of stuffing their faces with junk, and drinking loads of beer. Thus, gaining weight back, whining about it, and then living off of chips and beer for the next month.
Honestly, it's annoying, and confusing. They're both weight-obsessed, fat-hating people, so you would think they would be happy, even encouraging, towards their chubby daughter trying to lose weight? But, no. They mock my dieting, AND my weight. I don't get it!! I've been looking for apartments recently, and I have this one friend who I could be possible roommates with (meaning I can get out of this dump quicker), but it's going to still be a decent length of time before I move out. Until then, I'm going to have to put with my parent's constant mockery. It's not the mockery itself- it's the question "Why?" that's worse. I just don't get it. Does anyone else know anyone like this? Why do they act like this? If anyone has any answers, please tell me. I'm just sick of my parents senseless mean comments towards my attempts at a healthy lifestyle. This isn't the first time they've been mean at me for doing something I thought would've pleased them, and I'm beginning to think they're just hateful people who are looking to hate on whatever they can.