Carp Speedster Kosuke Tatsumi's Remarkable 3% Body Fat Helps Fuel His Record-Breaking Pinch-Running Success

Hiroshima Carp infielder Kosuke Tatsumi has established himself as one of baseball's most dangerous pinch runners, and on September 3 he reached a milestone that had stood for nearly half a century.

With Hiroshima leading the Chunichi Dragons 5-2 in the seventh inning at Vantelin Dome, Tatsumi entered the game as a pinch runner and promptly stole second base.

It was his 25th stolen base of the season as a pinch runner, tying the NPB record set by Fumiaki Fujise of the Kintetsu Buffaloes in 1979. Tatsumi has 26 steals overall this season, meaning all but one have come in a pinch-running role.

For Tatsumi, the achievement is the product of an almost obsessive dedication to the craft of being a pinch runner.

He underwent genetic testing during the offseason to determine what his ideal body weight should be. The result was 65 kilograms, and because he naturally tends to lose weight easily, Tatsumi takes four different supplements regularly to make sure he gets enough vitamins and other nutrients.

Every detail is designed around one specific job: being as effective as possible over the 27.431 meters between first and second base.

His body composition is particularly remarkable. Tatsumi's body fat percentage is just 3%, an extraordinary figure in professional baseball, where the average is believed to be around 15%.

Even Ichiro, who was known for his exceptional conditioning during his playing career, was reportedly around 6–8%.

“I've never heard of another Carp player having a body-fat percentage that low.”

That is the assessment of Hiroshima trainer Shinji Miura.

Such an extremely low body-fat percentage can also carry risks, including a greater susceptibility to illness caused by reduced immune function. But for Tatsumi, it gives him a physical advantage he is unwilling to sacrifice.

“It's easier for me to control my body exactly the way I want.”

Since joining Hiroshima, Tatsumi has also embraced headfirst slides, continuing to refine his technique on a daily basis.

His preparation doesn't stop with his physical conditioning. He has become increasingly skilled at studying opposing pitchers, particularly at the beginning of a series, looking for subtle tendencies that could give him an advantage when he gets on base as a pinch runner.

Yet despite tying a long-standing professional record, Tatsumi insists there is still plenty of room for improvement.

“There are still so many things I can improve.”

Tatsumi joined Hiroshima through the 2025 active-player draft after spending the previous three seasons with the Rakuten Eagles organization.

A 2022 developmental draft first-round pick out of Seinan Gakuin University, he was promoted to Rakuten's regular roster in July 2023. After being re-signed as a developmental player following the 2024 season, he returned to the regular roster in July 2025.

He stole 31 bases in the Eastern League last season, leading the league in stolen bases, before moving to Hiroshima during the offseason.

Tatsumi's unusual approach to athletic development even extends to an unlikely source of inspiration: snakes.

During voluntary training on Amami Oshima in January 2025, he encountered a habu and was fascinated by the way it moved.

“It doesn't have arms or legs, but it's fast and strong. I want to move like a habu.”

The encounter strengthened his focus on developing his core and improving the way he controls his body.

Away from baseball, Tatsumi is also an avid reader and even wrote his own novel during his final year of high school.

His personal philosophy reflects the same mindset he brings to his unusual role on the baseball field:

“Don't worry about choosing the right path. Live in a way that allows you to believe the path you chose was the right one.”

Now just one stolen base away from taking sole possession of the NPB record for pinch-runner stolen bases in a season, Tatsumi continues to push the limits of what a specialist can accomplish.

For a player whose entire role can be decided in a matter of seconds, he has made sure that virtually everything—from his body weight and nutrition to his sliding technique and study of opposing pitchers—is designed to make those seconds count.