Actresses have to remain slender to qualify for most-k-drama roles but occasionally they also have to bulk up. And it's harder than you might imagine.

For example, slim attractive Go Ara was considered too slim and pretty to play the role of Na Jeong in "Reply 1994."

"The director asked me if I would be okay with ruining my image and I was prepared," she said.

She cut her own hair with a knife and gained weight. But adding pounds was harder than expected.

"The director kept telling me that I had to gain weight," she said. "The most I could gain was nine pounds but Na Jeong had a good appetite so I gained 15 to 18 pounds as filming continued."

Go Ara is not the first k-drama actress to gain weight for a role. Kim Sun Ah gained 15 pounds to pay the role of Kim Sam Soon in "My Lovely Kim Sam Soon."

It was an important part of presenting the pastry chef heroine, who her ex-boyfriend describes as smelling like sugar.

"It was not pleasant for me as an actress," said Kim Sun Ah. "But I regarded the fat around my stomach as a way to express Sam Soon's inner state.

The secret of a successful drama, says Kim Sun Ah, is for the audience to sympathize with the main character.

"If I looked beautiful, would the viewers have sympathized with me as much," she asked.

When movie roles call for a huge weight gain, actresses will occasionally put on a silicon body suit. Kim Ah Joong relied on makeup for her transformation in the film "200 Pounds Beauty" but declined the offer of doing a sequel when it was suggested that she gain actual weight for the role. IU wore a weighty costume to add bulk in "Dream High."

But some actresses prefer a more realistic approach. When actress Lee So Jung took the role of a model that gained weight in the 2012 film "Plump Revolution," she put on almost 50 pounds. The unique slant of the story interested her. There are plenty of stories about an overweight girl losing weight and finding love but she knew of none where it worked the other way around.

"I was intrigued by the character who decided to gain weight for love," said Lee So Jung.

Because she does not gain weight easily, it was difficult. She had to eat 10,000 calories every day and the kinds of food she normally never ate. That dedication actually made her sick.

"I was impressed by her effort," said her co-star Lee Hyun Jin.

Gaining weight may sound like fun but it can be hard work for those accustomed to being slim.