do they really only eat 800 calories a day?

No probably not. They're Korean. It's in their genes to be SO skinny. They probably have big appetites, I don't know. You've also gotta think about their schedule. They dance their butts off 24/7 and they're always performing. They work out alot to keep their figures and probably do eat alot of healthy stuff.
If wewe want to lose weight a healthy way I suggest a 1200 calorie a siku diet with plenty of excercise. 800 calories is an anorexic calorie intake.

no... they dont.. it was just a rumor.. SM entertainment denied it :)

Not really.I think almost all the singers in the world are slim for their image but I don't think they eat less than let's say 1500 calories