If you’ve been keeping up with Jersey Shore Family Vacation, you may have noticed that Jersey Shore alum Vinny Guadagnino has been working out and eating well. Remember that episode when he only ate the cheese off a slice of pizza? There was a reason for that! He attributes his weight loss to the keto diet, even calling himself a "keto guido."

In a recent Instagram post, the 30-year-old shared an impressive before and after picture championing his new lifestyle. “I never posted a photo from when I was overweight, because it always embarrassed me putting it out there to millions,” he wrote. “But I know that it will help and inspire people, because I looked for the same body transformations when I was trying to lose weight and be healthy so f–k it.”

So, what is this trendy weight loss diet that he and other celebs (e.g. Halle Berry and Kim Kardashian) swear by?

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I never posted a photo from when I was overweight because it always embarrassed me putting it out there to millions , but I know that it will help and inspire people, because I looked for the same body transformations when I was trying to lose weight and be healthy so fuck it . _ On the left you have chunky Vinny . Chunky Vinny eats a lot of bread, pasta , pizza , fried food, and sugary desserts and is always hungry . He goes on diets and eats “whole wheat” pasta , quinoa and “whole wheat pizza crust to try to be healthy. He does juice cleanses, tries to eat in small amounts.. etc .. goes to the gym occasionally but is always tired and lacking energy and ..somehow he always gets back to the pic on the left. _ On the right you have the #ketoguido. He doesn’t eat any bread , pasta , or grains (whole wheat or not) and no sugary foods. He reads the labels of everything he eats to make sure there aren’t hidden sugars in them. He doesn’t count calories, he eats fatty delicious food , grease , vegetables never feels deprived , is rarely hungry ,has a cheat meal once in a while, is full of energy and mental clarity and exercises several times a week . Keto Guido never has to go on a quick fix diet again because his “diet” already is a diet for life. PS : people who think I’m too skinny . ( I don’t care what u think) and the “skinny” guy on the right FEELS BETTER than the guy on the left . I’m also not a body builder . I work out to stay healthy and happy. Sorry chunky Vinny Lovers , #ketoguido is here to stay. _ PSS: the pic on the left was in 2015. The right is 2017. It didn’t take me two years to make that transformation . (Took me about 3-4 months) to get in good shape . But just chose an old photo for the chunky example

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Like Atkins, the keto diet is all about cutting carbs — with the idea that without carbs, the body will start a process called ketogenesis, breaking down fat into an energy source. Therefore, you can eat meats, leafy greens, above-ground veggies, high-fat dairy, nuts, seeds, and sweeteners; but you have to avoid most grains, sugar, fruit, and root vegetables. "Try to remember that keto is high in fat, moderate in protein, and very low in carbs," a Ruled.me explainer says. "Your nutrient intake should be something around 70% fats, 25% protein, and 5% carbohydrate."

But as Vox points out, the keto diet is based only on a scientific hypothesis, and studies of low-carb diets suggest they don't outperform other diets in terms of long-term weight loss. (In the short term, the keto diet can seem effective because it causes rapid water loss and perhaps even controls appetite.)

Plus, a lot of people have trouble staying on the diet. "Randomized controlled trials don't lie," blogged obesity researcher Stephen Guyenet. "The average person can't even stick with the diet for six months, as judged by urinary ketone levels. The minority of people who find it easy, get good results, and stick with it are the ones who write about it on the Internet."

A few years ago, National Institutes of Health researcher Kevin Hall conducted what's considered the "gold standard" study of ketogenic weight loss and found that the keto regimen didn't burn the pounds as effectively as a higher-carb diet. "The idea is that low-carb, ketogenic diets cause your body to burn way more calories, resulting in a lot of weight loss, even if you eat more than you were eating before," he told Vox. "But our studies, as well as many others, demonstrate nothing of the sort."

Still, Vinny is a huge proponent of the diet, so perhaps he's in the minority of folks who have successfully vetoed carbs and keto-ed themselves into shape. And if he's healthier as a result, more power to him!