In the world of acting, physical transformation often becomes a necessary part of the craft. But few do it with the quiet intensity and discipline of Park Seo-joon. Known for his versatility, charm, and commanding screen presence, Park stunned audiences with his lean and sharp appearance in the hit drama “Itaewon Class”.
Behind the scenes, however, this transformation required more than just good lighting and styling. To accurately portray Park Sae-ro-yi, a determined and street-hardened young man, Park Seo-joon undertook a strict low-calorie diet and disciplined lifestyle changes, ultimately losing 15 kilograms (approximately 33 pounds) over the course of a year.
His story isn’t just about aesthetics, it’s about what happens when a performer commits fully to embodying a character, with precision, patience, and an unshakable work ethic.
Becoming Park Sae-ro-yi
Itaewon Class is a story of grit, rebellion, and ambition. Park Seo-joon played the lead role of Park Sae-ro-yi, a character shaped by loss, resilience, and years of physical labor. To make the role believable, he needed to strip away any softness from his appearance and present a physique that reflected endurance, struggle, and restraint.
Park himself has said in interviews that this was one of the most physically demanding preparations of his career not because of training, but because of how much he had to reduce his food intake while maintaining energy for long filming days and rehearsals.
Low-Calorie, Nutrient-Dense, and Monitored
Park Seo-joon’s transformation relied primarily on a low-calorie diet designed to create a consistent calorie deficit over many months. His goal wasn’t extreme speed, but controlled, gradual fat loss that would not affect his performance or mental sharpness.
His diet likely consisted of:
- Lean protein sources such as egg whites, chicken breast, and tofu
- Steamed or raw vegetables to increase fiber and volume without adding calories
- Minimal carbohydrates, primarily from sweet potatoes, brown rice, or fruit
- Virtually no processed foods, sugars, or fried items
- Careful portion control, with frequent small meals to prevent hunger spikes
This kind of regimen requires mental toughness, especially in the entertainment industry where long hours, physical exhaustion, and social obligations make it easy to fall off track. Yet Park stayed consistent for nearly a year.
To maintain muscle mass and avoid nutritional deficiencies, he likely included essential supplements like BCAAs, vitamins, and perhaps meal replacements when needed.
The Physical Outcome
By the time Itaewon Class premiered, viewers immediately noticed the physical transformation. Park Seo-joon’s jawline was sharper, his shoulders more defined, and his overall physique reflected the rough, resourceful energy of his character.
The change wasn’t dramatic in a superhero way, it was realistic and grounded. He looked like someone who had spent years working hard, skipping meals, and surviving life on the edge. His appearance added emotional weight to the role, deepening the audience’s connection with Park Sae-ro-yi.
The Psychology of Self-Denial
What makes Park Seo-joon’s transformation especially impressive is the emotional and psychological restraint it required. For many actors, dieting under pressure can lead to fatigue, frustration, and even burnout.
Yet Park approached the challenge like a professional athlete. He didn’t treat it as a burden, he treated it as part of the process. He understood that embodying a character requires sacrifice, not just in script memorization but in physical presentation.
This mental discipline, paired with his quiet consistency, became the real engine of his transformation.
Life After the Role
After Itaewon Class, Park Seo-joon gradually returned to a more balanced lifestyle adding back healthy calories, increasing his training intensity, and allowing his body to recover from months of restriction.
Unlike crash diets that often result in rebound weight gain, Park’s structured approach allowed him to exit the transformation phase smoothly, preserving muscle tone and maintaining overall health.
His ability to shift from low-calorie discipline back to long-term sustainability demonstrates his understanding of body science and his commitment to preserving both his performance and well-being.
What We Learn from Park Seo-joon’s Transformation
Park Seo-joon’s journey isn’t about a celebrity getting “shredded” for the camera. It’s a story of deliberate, artist-driven transformation, marked by patience and purpose.
Key lessons from his process:
- Weight loss takes time even for celebrities. One year for 15 kilograms is realistic and healthy.
- Discipline beats motivation. Daily commitment is more important than momentary excitement.
- Food is fuel. Even on low calories, nutrient density matters more than volume.
- Physical change supports emotional storytelling. Appearance can help actors deepen their connection to their roles.
- Recovery is essential. Extreme changes must be followed by balanced habits to prevent burnout.
Ready for Your Own Transformation?
Whether you’re preparing for a professional goal, seeking better health, or just want to feel lighter in your own body, Park Seo-joon’s journey proves that long-term, structured transformation is possible with the right mindset and method.
At Erdem Hospital, we guide international patients through safe, medically supervised weight loss programs including low-calorie meal planning, metabolism monitoring, and post-diet recovery support. Like Park, you don’t need to rush. You need to be strategic, consistent, and supported.
Frequently Asked Questions (FAQ)
How much weight did Park Seo-joon lose for Itaewon Class?
He lost approximately 15 kilograms (33 pounds) over the course of a year to embody the character of Park Sae-ro-yi.
What kind of diet did he follow?
Park followed a low-calorie diet, likely rich in lean proteins, vegetables, and minimal carbohydrates. He eliminated processed foods and practiced portion control.
Did he combine the diet with exercise?
While details are limited, he likely included moderate strength training or bodyweight workouts to preserve muscle mass during weight loss.
Was this transformation extreme or gradual?
It was gradual, taking place over one year making it both safe and sustainable.
How did he avoid weight rebound after filming?
He gradually reintroduced calories, returned to a balanced diet, and increased his physical activity to maintain long-term results.
Is this type of transformation realistic for non-actors?
Yes. With professional guidance, anyone can achieve similar results especially when the focus is on realistic timelines and structured support.
Where can I find support for a similar transformation?
Erdem Hospital offers customized low-calorie weight loss programs for international patients, combining nutritional planning, medical supervision, and aftercare for sustainable results.