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

New England Patriots' Rob Gronkowski speaks with members of the media during a news conference Jan. 30, 2019, ahead of the NFL Super Bowl 53 football game against Los Angeles Rams in Atlanta. (AP Photo/Matt Rourke)

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

Nov 20, 2016; Cleveland, OH, USA; Cleveland Browns tackle Joe Thomas (73) during the second quarter against the Pittsburgh Steelers at FirstEnergy Stadium. Mandatory Credit: Scott R. Galvin-USA TODAY Sports

Cleveland Browns tackle Joe Thomas (73) during the second quarter against the Pittsburgh Steelers at FirstEnergy Stadium in 2016. (Scott R. Galvin-USA TODAY Sports)

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

TEMPE, AZ - CIRCA 2010: In this handout image provided by the NFL, Alan Faneca of the Arizona Cardinals poses for his NFL headshot circa 2010 in Tempe, Arizona. (Photo by NFL via Getty Images) *** Local Caption *** Alan Faneca

In this handout image provided by the NFL, Alan Faneca of the Arizona Cardinals poses for his NFL headshot in 2010 in Tempe, Ariz. (Photo by NFL via Getty Images)

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

Baltimore Ravens Matt Birk, and Gino Gradkowski talk during football practice Saturday, Jan. 26, 2013 in Owings Mills, Md. (AP Photo/Gail Burton).

Baltimore Ravens Matt Birk, right, and Gino Gradkowski talk during football practice Saturday, Jan. 26, 2013 in Owings Mills, Md. (The Associated Press)

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

KANSAS CITY, MO - DECEMBER 10: Guard Will Shields #68 of the Kansas City Chiefs gets ready to block in a game against the Baltimore Ravens at Arrowhead Stadium on December 10, 2006 in Kansas City, Missouri. (Photo by Tim Umphrey/Getty Images)

Guard Will Shields #68 of the Kansas City Chiefs gets ready to block in a game against the Baltimore Ravens at Arrowhead Stadium on December 10, 2006 in Kansas City, Missouri. (Photo by Tim Umphrey/Getty Images)

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.