According to former girl group trainees who have experience training in various entertainment agencies, there is a common "formula" for determining the "ideal weight" that K-Pop idols must meet prior to their debut.

For girl groups, the "formula" is: (Your height in centimeters) - (120) = the ideal/goal weight. 

According to the former trainees, the reason that idols follow stricter weight regulations prior to their debut is so that they can appear "ideally pretty" on camera. 

"You have to be at the point that people around you will say, 'That girl is too thin!!!!!!', for you to appear 'pretty' on TV," the trainees said. 

However, once idols debut, weight restrictions are lifted to a certain degree, as K-Pop groups often carry out rigorous schedules which require a great amount of energy. 

But many netizens felt that this formula was unrealistic, and commented, 

"It sucks but it's true that on camera, everyone looks fat. Especially broadcast cameras make you look at least 140% bigger than you are."

"So if I want to debut, I need to lose like 14 kg? Not gonna happen."

"That means anyone who is in the 150 cm range needs to be in the 30 kg range... a.k.a just die??"

"This is why when you see K-Pop idols in real life, they are literally stick thin."

"39 kg???? I haven't been that weight since I was a child."

"Those cameras are the problem. They make people look huge."

"Can they please just invent better cameras, like seriously so many K-Pop idols eat next to nothing because of those cameras."

"If normal people went by that formula, they would have to just give up their health completely."

"This is why a lot of K-Pop idols were just born to be K-Pop idols... They have naturally thin bone frames."