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She has stunned millions of viewers with her jaw-dropping weight loss transformation. Former 450-pound reality star June Shannon is now an impressive size 4 after months on a strict diet, a grueling exercise regime and thousands of dollars worth of plastic surgery.

Now the celebrity trainer who worked with the mom-of-four on WE tv’s hit “Mama June: From Not to Hot,” is revealing what it was really like whipping the 37-year-old into shape. From pretending to go on 2 a.m. jogs to refusing to work out even though two-hour sessions had already been scheduled, Natasha Fett says Shannon (who has lost close to 300 pounds) kept her on her toes.

“Every day, all day there’s something going on with June,” says the Los Angeles-based trainer and nutritionist who has worked with the likes of Matthew McConaughey and Fergie.

“Mama June is known for not doing what anybody tells her to do. She kind of has a thick head and she would basically a lot of times not tell me the truth about what she would do.”

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For Fett, it was hard to monitor her moody client who is located thousands of miles away in Hampton, Ga. That gave Shannon plenty of opportunity to fib about whether or not she was sticking to her plan – that included allegedly lying about when, how long, or even if she was working out.

“She would tell me, ‘I went running at 2 in the morning,’” says Fett who used to check in on her client remotely via a smart phone exercise app. “I’m like, ‘No June. No you didn’t work out at two in the morning. Stop talking s**t.”

In the show fans saw Shannon pretend to go on a long jog while driving around in a car, leaving the workout app on her phone running. But Fett says that didn’t just happen once, but many times and the reality star would stick to her guns saying she had actually done the workout, even when confronted.

“At some point in the evenings I would check on the app to see how much she’s done and it would be like usually about 2.5 to 3 miles. Then all of a sudden it was like 6 or 12 [miles] at a 4-minute/mile pace or something crazy,” says the German-born trainer. “I’d be like, ‘What happened? You became a professional runner?’”

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Fett says Shannon kept doing it even though she called her out for “driving around” and “faking…workouts.” The trainer says: “She’d do that quite often where she would just have the app on and do a loop, be in a different town and drive somewhere else.”

In “Mama June: From Not to Hot,” an exasperated Fett had to get an Atlanta-based trainer, Kenya Crooks, to babysit her client. She says: “She would just make up stuff or try to skip workouts or eat stuff she’s not supposed to eat. She would say, ‘I didn’t do that. I didn’t eat that. I only had so much.’”

Fett, who would send Shannon supplies of her own range of protein shakes and juices, says: “I’d come to the house and she’s dipping salmon into ketchup. I’d literally catch her doing it. So you really have to have her on such a tightrope.”

Things weren’t any easier for Fett when she worked with Shannon during the former “Here Comes Honey Boo Boo” star’s trips to LA. The trainer says that even though they’d schedule two-hour workout sessions – sometimes as early as 5 a.m. – she would turn up and Mama June would just suddenly decide she wasn’t going to exercise that day.

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Fett, who is also an executive producer on the show, says that Shannon prefers to do things her own way. She says: “[June’s] not someone you can say, ‘Go wait over there until I’m ready for you.’ She’s not that person. She’d be like, ‘What the f**k?’ She’s really headstrong.

“When we’d exercise while she was here in LA, I would go to pick her up and she’d have all kinds of excuses why we can’t leave right now. She’s got all kinds of things to do.

“You don’t tell her, ‘No we have to do this. We have a deadline.’ She’d shutdown. She’d be like, ‘Your problem. I don’t really care.’”

Fett, who would have the mammoth task of trying to get her difficult client to comply, adds: “She’d be like, ‘I only have 20 minutes today because I have something to do.’ Sometimes she would say, ‘I don’t even understand why we have to meet so often.’ So I’d remind her that we have a goal and in order for us to get to the goal we have to do this.”

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“Mama June: From Not to Hot” has been a ratings bonanza for WE tv premiering in February with 2.3 million total viewers, making it the cable channel’s biggest premiere ever. Ironically though, when Fett first met Shannon back in 2015 it wasn’t to work with her at all but with a then nine-year-old Alana Thompson, aka Honey Boo Boo. Mother and daughter had just been on daytime show “The Doctors,” during which the presenters warned that the child was obese.

Asked by Mama June’s manager Gina Rodriguez to educate the family on healthy living, Fett would make fortnightly visits to Georgia. She’d take them on hikes, trips to the grocery store and teach them how to actually cook rather than eat just fried, junk or frozen processed food that could be zapped in the microwave.

But whereas Honey Boo Boo would barely lose one pound in two weeks, Shannon would shed eight. So the trainer told the manager: “We should just focus on Mom so that Mom can parent the kids and get them on the right track.”

Fett says she knew hardly anything about Shannon and her family. At the time Mama June was without a show after TLC canned the hugely successful “Here Comes Honey Boo Boo” in 2014 when a photo of the matriarch in bed with her ex-boyfriend Mark McDaniel emerged. There was a huge uproar when it was revealed that he served time for molesting her eldest daughter Anna “Chickadee” Cardwell when she was just eight.

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But, despite that controversy, Fett says that whenever she has been out in public with Shannon fans mob the mom-of-four. For the celeb trainer who is used to running with Hollywood celebs, it was an eye opener to see people clamor around the controversial reality TV star.

Fett says: “Everywhere I would show up with her, people would be crazy with her – crazy in a good way. They would love her and follow us to the airport, follow us in New York, wanting to take pictures with her.

“It’s so different. I run with Matthew McConaughey and people are very discreet, so they look but they kind of step back. I don’t really get as much attention as when I’m just walking from terminal to terminal with Mama June. It’s like you’re walking with Michael Jackson. Seriously.”

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As for how the transformation has affected her client, Fett says that it hasn’t been just a physical one but a mental one too. The potty-mouthed Shannon, who used to slyly cheat on her plan, now enjoys eating healthily, loves what she sees in the mirror and is “very pleasant to be around.”

“She’s very friendly because most of it’s accomplished and done,” Fett says, later adding: “She’s definitely friendly and bubbly and laughs and is happy.”

First published on the New York Post.