Dada Chan heeded the advice of the movie director to put on 8kg to portray a pregnant character in The Secret Life Of A Mum To Be.
But her health suffered when she had only a month to shed the excess weight after she was given another film role.
According to Ming Pao, Chan, 30, said: "I will never do it again."
In a fight against time, she revealed that she had only one meal every day, and even then, she cut back on the portions.
Despite the caloric shortfall, she still exercised diligently, and she soon paid the price.
"My health deteriorated," Chan said, adding that she is now taking herbal medicine to bounce back.
The actress also suffered a health scare in 2017 when work stress made her dizzy.
On why that lesson of taking a year off from work had not sunk in, Chan said sacrifices are sometimes necessary in fleshing out a character more realistically on screen.
Admitting that she was close to tears after she noted how swollen she looked after her weight gain for The Secret Life, she said she channelled that distress in portraying her character's coming to terms with a new phase in life.
Her dedication has paid off, with a South China Morning Post reviewer saying: "After a string of supporting roles of the decorative kind, Chan seizes her moment in the spotlight with a dramatic performance that finally allows her to demonstrate her range."