Jake Gyllenhaal has the best body in Hollywood. A celebrity trainer says his fitness discipline is unparalleled.

• Jake Gyllenhaal's ripped body in upcoming film "Road House" stunned people earlier this year.
• His trainer told Insider that Gyllenhaal's dedication and commitment is unparalleled.

Jake Gyllenhaal stunned the internet with his ripped physique when footage of him filming a topless weigh-in scene for upcoming movie "Road House" was shared in March 2023.

Gyllenhaal is starring in the upcoming Amazon Prime remake of the 1989 movie and filmed scenes for it at MMA event UFC 285 in Las Vegas.

Gyllenhaal's long-time trainer Jason Walsh told Insider that getting him in shape for the film wasn't hard because he's "the perfect specimen" whose level of commitment and dedication is unparalleled.

Walsh, who has also trained Matt Damon, Jessica Biel, Miles Teller, Brie Larson, and Bradley Cooper, said Gyllenhaal is always active — outside of the gym, he loves tennis, swimming, and cycling — and has to be told to take a rest day.

Gyllenhaal's weakness is sugar

Walsh has been working with Gyllenhaal for eight years now which meant they weren't starting from scratch for "Road House."

Often celebrity trainers have very little time to get an actor ready for a movie, but this isn't a problem with Gyllenhaal because he was already in good shape, Walsh said.

"If he's not in the gym doing strength training and conditioning, he's swimming, he's outside playing paddle tennis, he cycles like crazy," Walsh said. "The guy does everything. He's just always looking for that stimulus."

The trainer asks his clients to keep themselves within three weeks of getting back in shape in case a movie or project comes up last-minute.

They aimed to fine-tune Gyllenhaal's body based on when the shirtless scenes were going to be filmed, but, Walsh said, the actor is "the perfect specimen," meaning Gyllenhaal makes Walsh's job easy.

Gyllenhaal also worked with a dietitian and chef to make sure his nutrition was on point.

His one weakness is sugar, Walsh said — but consuming carbs and sugar is actually necessary to tone up: "When your body fat gets to a certain level, you need fuel and a constant trickle of energy because you don't have stored energy, i.e. fat."

VersaClimber workouts helped him get shredded

As well as workouts in the gym, Gyllenhaal went to VersaClimber classes at Walsh's fitness studio, Rise Nation, in New York, Walsh said.

"He was going there a lot especially since we were trying to get him into UFC fighter shape," he said.

Versaclimber workouts mimic our primal climbing and crawling movements and are an effective way to boost cardiovascular fitness, but simply sweating and getting your heart-rate up is not necessarily the sign of a good workout, Walsh said.