Actor Joo Ji Hoon recently opened up about the challenges he faced while preparing for his role in the movie 'Unofficial Operation.' 

During an appearance on KBS Cool FM's 'Park Myung Soo's Radio Show,' which aired on August 3, Joo Ji Hoon discussed his experiences while filming the recently released movie.

In the film, Joo Ji Hoon portrays a taxi driver who seeks customers in an area devoid of Asians. To embody the character convincingly, he dedicated himself to the role by exercising rigorously and intentionally gaining 12 kg (26.4 lbs) in weight. He shared, "My character is a taxi driver who solicits customers in a region where there are no other Asians. So I thought my character needed to stand out and should be big so no one would view him as an easy target."

However, the drastic weight gain took a toll on his health, and he candidly admitted to facing several side effects as a result. Joo Ji Hoon mentioned, "It wasn't easy to suddenly adjust my weight for the role." Following the filming, he managed to shed around 6 to 7 kg.

Regrettably, the process of gaining and losing weight repeatedly, coupled with the natural aging process, had negative consequences on his well-being. He revealed that he developed an immune disorder, which led to issues like gout and tinnitus.

Despite the challenges, Joo Ji Hoon's dedication and commitment to his craft were evident in 'Unofficial Operation,' a movie based on a true story of a diplomat's kidnapping in Beirut, Lebanon, back in 1986. 

The film follows the journey of Min Jun, played by Ha Jung Woo, a diplomat who ventures to Lebanon to rescue a missing colleague. There, he encounters Pan Su, portrayed by Joo Ji Hoon, a Korean taxi driver who becomes entangled in a dangerous situation.