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/ Source: TODAY
By Gina Vivinetto

Vinny Guadagnino is showing off his new buff bod — and it's all thanks to his ketogenic diet.

The "Jersey Shore" star, 31, took to Instagram over the weekend to share shirtless before-and-after shots showing off his fit new physique, which finds him 50 pounds lighter.

The popular keto diet is high in fat and features almost no carbohydrates. It allows dieters to burn fat for energy rather than carbs, resulting in weight loss.

Guadagnino is such a keto devotee, he launched the separate @ketoguido account in October 2017 to invite fans to follow along on his weight loss journey.

The reality TV vet shared his newest pics as part of the #10YearChallenge on social media that invites users to post photos of themselves from 2009 and 2019.

"As you know from all the before and after pics on this profile, I’ve had some fat unhealthy years in between," he wrote in one caption. But, he said, "eating natural fat, protein, and veggies instead of processed sugar and carbs has brought me back to (age) 21."

He cheekily captioned one pair of pics, "Sorry, Jill," in reference to celebrity trainer Jillian Michaels' recent concerns that followers of the trendy diet were "starving" themselves.

According to the former "Biggest Loser" coach, the keto diet doesn't provide proper nutritional balance.

"Your cells, your macro molecules, are literally made up of protein, fat, carbohydrates, nucleic acids,'' she said. "When you do not eat one of the three macro nutrients — those three things I just mentioned — you’re starving yourselves," Michaels said in a video for Women's Health.

Still, Guadagnino's hardly alone in his keto enthusiasm.

Many other celebrities, including Halle Berry, Kourtney Kardashian and TODAY's own Al Roker have praised the diet.

In the wake of Michaels' critical remarks last week, Al, who began the diet in September, said the decision to go keto should be an individual choice.

"My point is, what works for you, works for you,'' Al said during Friday's episode. "There's science on both sides that says it's not a great idea and science that says it is a great idea."

He added, "I think it's up to people, with their doctor, with their medical professional (to make their own decision)."