A healthy and not extreme kpop diet I have found. ^_^
However theres not much information on it. >.<
Gayoon lost 8kg (17.6 lbs) during the 2YOON promotions. The diet they were on, was done alongside exercising. She stated that "If you dance '24/7' just two times, you start sweating a lot."
Lunch: Sweet potatoes and boil chicken breast everyday
Exercise: 24/7 dance routine twice or more and aerobic exercises
Here is a video of the live performance, so you can see the 24/7 choreography