Actor Yoon Si Yoon shocked viewers with his intense weight loss transformation on the June 22, 2025, episode of SBS’s My Ugly Duckling, revealing that he had lost 5kg in just one day through an extreme no-water diet.
Preparing for his upcoming role in Taxi Driver 3, Yoon shared that he wanted to present a dramatically different look.
“I want to show a new texture to my character — something sharp and hollow, like I’m completely worn down.”
Determined to embody the role, he embarked on a 24-hour no water day, cutting out all liquids to push his body to its limits.
At the start, the actor weighed in at 67.4kg (148.6 lbs) with a body fat percentage of 6.7%. To survive the day without water, Yoon crafted a strict “zero-moisture” meal using only dried tofu and asparagus, known for its diuretic properties.
After a full day on the diet, Yoon reweighed himself and stunned everyone with his results: 62.3kg (137.3 lbs) and a body fat percentage of just 3.6%.
Yoon also visited a photo studio to test whether his new, sharper look came through on camera. Just three days before his shoot, Yoon pushed his body further, intensifying his workouts to sweat out even more weight. He even entered an extreme 45°C sauna for complete dehydration, soaking in hot water for 20 minutes like a UFC fighter to expel the last bit of water weight. Here are the amazing results.
Though his methods sparked concern, fans and cast members couldn’t help but be amazed by his level of commitment. Yoon Si Yoon’s transformation proves that when it comes to acting, he’s willing to go to extreme lengths to get into character.
