Not so fast!

Mike “The Situation” Sorrentino is firing back at folks who claim his newer fit physique is the product of steroid use.

After the official “Jersey Shore” Instagram account shared a photo of “X-Men” star Hugh Jackman posing with “Jersey Shore: Family Vacation” stars Nicole “Snooki” Polizzi and Angelina Pivarnick, Sorrentino, 37, felt it necessary to inform a commenter who suspected him of using performance-enhancing drugs that his results are due to a myriad of factors, none of which include steroids.

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“I am flattered you think I am on performance enhancing substance but I am not,” Sorrentino wrote. (via Us Weekly) “I am on probation and get tested biweekly for illegal substances. What you see is hard work, determination, proper diet, exercise, muscle memory, intermittent fasting, prison and genetics. You should try it sometime!! People love to throw shade on what shines. Stay in your own lane and run your own race cuz!! Do you even lift !? #clapbackseason.”

Sorrentino, who has dropped 35 pounds, detailed his prison regimen during an interview with Entertainment Tonight in September after he was released following an eight-month stint behind bars in Otisville, N.Y. for tax evasion.

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He said he worked out several times a day, starting at 7 a.m., and practiced intermittent fasting.

“I had to continually challenge myself, whether it was in the gym and/or diet,” the MTV star said. “I worked out between two to three times per day.”

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Sorrentino said his fierce exercise regimen helped pass the time and stay positive. He hit the gym on holidays when he was alone and said he wanted to “do something to make my future self proud.”

After his release, Sorrentino shared an image to Instagram showcasing his new-and-improved muscle structure while back in a civilian workout gym.

Mike "The Situation" Sorrentino and wife, Lauren Pesce.

Mike "The Situation" Sorrentino and wife, Lauren Pesce. (Jerod Harris/Getty Images for WE tv)

“This is what it looks like when you turn a negative Situation into a Positive Situation  #clapbackseason,” the entertainer captioned the photo.

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The reality star was released on Sept. 12 and celebrated the next phase of his life with a pizza party.

“We are elated to finally close this chapter of our life. Thank you to our family, friends and fans for the continuous love and support during this time, it brought us so much peace and comfort,” he said in a statement at the time.

Fox News' Jessica Napoli contributed to this report.