Inside Mike 'The Situation' Sorrentino's Prison Diet and Workout Routine (Exclusive)

In his first interview since leaving prison, the reality star explains how he stayed busy while in confinement.

Mike "The Situation" Sorrentino is a completely changed man after prison, mentally and physically.

In his first sit-down interview since leaving the Federal Correctional Institution in Otisville, New York, on Sept. 12, the Jersey Shore Family Vacation star opens up about the diet and fitness routine he created for himself behind bars.

Sorrentino admits that he went a little crazy with what he was putting into his body in the weeks leading up to the moment he turned himself into the correctional facility back in January after pleading guilty to tax evasion. As seen on Jersey Shore, Sorrentino was binge-eating everything from fast food to soda and unhealthy snacks.

"The last meal, I was probably ordering some sort of fast food delivery, 'cause I was ordering everything," he recalls. "When you realize that your freedom is being taken away from you, you're like, 'You know what, I'm not going to get good food in prison, so I'm going to order McDonald's, Wendy's, Chick-fil-A.' We're turning up and living our best life, and I did that. I gained a couple of pounds, but I had the time once I was in prison to concentrate on being my best self and losing the weight."

Sorrentino reveals to ET that he lost over 35 pounds during his eight-month sentence. He showed off his toned figure for our cameras while posing outside our New York office:

So, how did Sorrentino make the drastic physical transformation happen?  "Intermittent fasting," he says.

"I went to sleep every night at 10 p.m. I woke up every morning at 7 a.m. and did fasted cardio for about an hour," he explains. "I was practicing intermittent fasting while I was in prison. My window of intermittent fasting was between 16 and 17 hours on the weekdays, and 18 and 19 hours on the weekends."

"I had to continually challenge myself, whether it was in the gym, and/or diet," he continues. "I was reading books, the Bible and trying to progress spiritually as well. Because if you do not keep yourself busy in there ... I saw a lot of guys that weren't doing those things and you saw depression and anxiety take control."

Sorrentino says that in addition to the fasting, he worked out "between two to three times" per day.

"On holidays, especially," he recalls. "Because, you know, on your birthday, or Easter or something, you're in your feels a little bit. You're like, 'You know what? Today I'm gonna do something to make my future self proud.' And I put in my three [workouts]." 

"I felt very accomplished staying busy in prison," he adds.

The hard work certainly paid off, and no one could be prouder than his wife, Lauren.

"Honestly, I didn't think he could get more positive," she exclaims. "When he went in he was already so positive, uplifting, looking at the bright side of every situation in life. And I think he even elevated to another level of that, with his level of patience and learning that. I could definitely use some more patience in life, so he inspires me to be like that a little bit more."

Sorrentino's brother, Marc, also pleaded guilty to tax evasion, but was given a longer sentence of one year. He's currently still incarcerated, but Sorrentino says he and his family already have plans to celebrate once he's released... with plenty of food, of course!

"We'll definitely have an awesome Sunday dinner ready when my brother gets home," he tells ET. "I'm sure my mom will make the meatballs and the sauce and she'll probably make some dessert. Actually, my mom, this Sunday is making a whole spread for me because I haven't gone over yet. We're going to have chicken cutlets, fettucini with peas and ham, baked clams, chicken cutlet salad, bread and antipasto."

Sorrentino adds that his brother is "doing good," and is hoping to get permission from his probation officer to pay him a visit soon. "Listen, it's a difficult situation, but at the end of the day, you have to rise to the occasion and continue to move forward," he says.