Not starving

So I had been doing so great with my weight loss.  I had lost 8 lbs a few weeks ago, but some people of facebook said that I needed to make sure that I was eating at least 1200 calories a day.  I had only been averaging about 800 a day.  When I bought that Jillian Michaels book, their advice was reaffirmed.  Eating less that 1200 calories a day really messes with your body.  Apparently causes a yo yo dieting effect where you lose considerable amounts of weight but if you go off that diet or eat more calories than you had been eating you gain back the weight plus more.  I experienced that this last week.  I didn't gain it all back, but pretty close.  I have taken 1 lb back off, but it makes it hard to not eat 800 calories a day when I see such amazing results.  I realize it's bad for my body, but I wanna lose weight quickly.  I am really having a hard time with it.  HELP!