Ahn Jae-hyun Gained 17kg and Now Does 1,000 Ab Reps a Day for One Scene

Actor Ahn Jae-hyun is putting in the kind of gym time that most professional athletes would recognize. On the 14th, he posted a video to his YouTube channel titled "Ahn Jae-hyun's Gym Life These Days," documenting a training routine that begins at 8:40 a.m. and, by the time weights, an hour of cardio, a shower, and a meal are accounted for, does not end until around 2:30 p.m.

The origin of all this effort is specific: Ahn said in an earlier interview that he started building muscle seriously after being cast in a project with a bed scene. His lowest recorded weight had been 60kg; he is now at 77kg, a 17kg gain that his current schedule is designed to refine rather than simply maintain.

1,000 reps before the real work begins

The detail that opens the video is the one that lands hardest. Ahn starts and ends each session with 1,000 ab repetitions. When the production crew asked why that particular number, he kept it short: "My abs need to show. Simple principle."

Those 1,000 reps, he explained, are only the warm-up. The main session includes side lateral raises, shoulder presses, and rear-delt work, each at high volume. His trainer added context: "Right now we're in a cutting phase, so the rep counts are high and the intensity is high too. Jae-hyun is just quietly grinding through it."

He goes seven days a week. In Korean fitness culture, that kind of frequency is usually reserved for competitive athletes or someone with a very firm deadline, and Ahn seems to be operating in the latter category.

The Brad Pitt benchmark

Ahn and his trainer have settled on a specific reference point for what the finished physique should look like. "What we're trying to build is Brad Pitt's body from Fight Club," the trainer said, "not excessive, but balanced in a way that anyone can see is well-proportioned." Ahn echoed that, saying he wants to appear broader, with particular attention to shoulders and abs.

The Fight Club benchmark is worth noting as an industry signal. It is a physique associated with visible leanness rather than maximum size, which maps directly onto what reads well on screen in a scene that requires a certain kind of exposure without tipping into bodybuilder territory.

Side effects: better skin, fewer beers

Ahn was candid about what the routine has displaced. He mentioned that his usual evening routine involved cold beer and a favorite streaming channel before falling asleep. That, he said, is essentially gone: "There's no room for beer anymore. I'm already full."

In its place: protein after training and an earlier bedtime. He also noted, with what read as genuine surprise, that his skin has improved since he started. At one point during the video, catching himself in the gym mirror, he joked that he occasionally falls into a kind of self-hypnosis: "Sometimes the hypnosis kicks in and I start thinking I look handsome."

It is a self-deprecating line, but the numbers behind the routine are not a joke. Four-plus hours a day, seven days a week, with 1,000 ab reps as the entry fee, is a serious training block for any project.