Michael Rubin admitted to using Ozempic competitor Mounjaro to obtain his newly fit physique.

The Fanatics founder posted a revealing photo of himself on Instagram Friday morning in honor of his 51st birthday and revealed it was his first “shirtless” picture since he was 15 years old.

“I may be old as s–t but it ain’t that bad!😂😂 ps thanks @ovoroxx for kicking my ass lately and obviously thanks to @mounjaro_us – without it I’d be the Pillsbury Doughboy lol,” Rubin captioned the photo, referencing the drug that is meant to treat diabetes.

He then joked “plastic surgery” would be his “next” step toward eternal youth before thanking his longtime girlfriend, Camille Fishel, for photographing him at his “finest this morning after getting caught in the rain.”

The comments section instantly lit up with his friends applauding his new look (and his new age).

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“You looked like diff person when I just saw you then from exactly a year ago. Look 10 years younger also,” wrote recycling guru Adam Weitsman. “On top of being more fit… Good work 💪.”

“Happy bday and I like this look. I know it well,” restaurateur David Grutman commented.

Rubin also flaunted his new body at his A-list Independence Day White Party in The Hamptons earlier this summer, where anyone who is anyone was seen enjoying themselves.

Kim Kardashian, who wore a 17-carat diamond belly chain to the bash, was spotted talking to single Tom Brady — though sources maintain they’re just friends.

Ben Affleck’s 17-year-old daughter Violet also made headlines for looking exactly like her mother, Jennifer Garner, while attending the party with her stepmom, Jennifer Lopez.

Of course, no party would be complete without Emily Ratajkowski showing up in a sheer dress and twerking her way through a room.

Rubin hosted the star-studded event at his $50 million Bridgehampton estate.

Rubin joins a long list of celebrities, including Sharon Osbourne, Amy Schumer and Elon Musk, using drugs made to treat diabetes for weight loss.