The NFL features players at the extreme peak of physical ability.

Offensive and defensive linemen usually weigh more than 300 pounds while tight ends and linebackers are built like trucks and have cheetah-like agility.

While these players are known for being big and tall, things begin to turn around for some of them upon retirement. Several players have had dramatic weight loss since stepping away from the game.

Below are some of the most shocking turnarounds from players who now look like a different person.

ROB GRONKOWSKI

Former New England Patriots tight end Rob Gronkowski retired in March and three months later he was seen sporting a slimmer look. The 30-year-old appeared at the premiere of Julian Edelman’s new Showtime program — and one could barely recognize the man who had been catching touchdowns from Tom Brady just a few months prior.

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According to Yahoo Sports, Gronkowski has been a subscriber of the TB12 Method, a weight-loss regimen created by Brady and the quarterback’s trainer Alex Guerrero. The regimen was a bit controversial because of the cans and cannots of the diet. Gronkowski at one point weighed 265 pounds.

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JOE THOMAS

Former All-Pro offensive lineman Joe Thomas retired from the NFL after the 2017 season. The former Cleveland Browns standout weighed 312 pounds at his peak but a photo earlier this year showed he had lost most of his playing weight.

“Facts: I think the first 25 fell off in a month, than I had to kick my butt to keep going. Swimming is the best from a cardio standpoint, and #keto w/ intermittent fasting is gold. I can eat 1500-2000 cals/day and feel full,” Thomas tweeted in March.

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ALAN FANECA

Alan Faneca played 13 seasons in the NFL with the Pittsburgh Steelers, New York Jets and Arizona Cardinals. He made nine Pro Bowls and received six All-Pro selections. At the top of his game, he weighed more than 300 pounds. But several photos of the former guard showed a dramatic change.

In 2014, Faneca posted a photo on his Instagram of himself after running a marathon. Those who commented on the post appeared to be shocked at the change.

MATT BIRK

Matt Birk played center for the Minnesota Vikings and Baltimore Ravens and was over 14 years in the league. He weighed as much as 310 pounds while racking up six Pro Bowl selections and a Super Bowl ring.

After retirement, Birk worked with Body By ViSalus and got onto a regimen that helped him lose a ton of weight.

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WILL SHIELDS

Hall of Fame offensive lineman Will Shields played 14 seasons with the Kansas City Chiefs and was one of the best guards in the game. He played every single game with the Chiefs, earning 12 Pro Bowl and two All-Pro selections.

He weighed 315 pounds at his peak, but recent photos have shown Shields sporting a different look.