From his days on “Parks and Recreation” to his leading role in “Guardians of the Galaxy”, Chris Pratt has undergone some major body transformations.

Now, the actor is sharing his workout routine on Instagram and inviting his followers to join him on his fitness journey as he gets in shape for a new role.

On Wednesday morning, Pratt posted videos of himself working out to Alicia Keys’ Girl On Fire and said, “It’s amazing when you find your UFC walkout song while you’re at the gym…I’ve been going for only 20 minutes now. Back’s a little messed up, so I’m just walking to start. But I’m sweating. As you can see, this girl is on fire.”

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Water, he said, is the key to weight loss: “If you’re like me and you’re wondering how you can just shed some weight: water.”

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The star admitted that he’s “got a ways to go” and “a lot of work to do” but revealed he had already lost 12 pounds.

Pratt will be starring in the film “Ghost Draft” alongside Yvonne Strahovski, J.K. Simmons, and Betty Gilpin. The sci-fi thriller takes place in a future in which humanity is at war with aliens.