The Biggest Loser former executive producer JD Roth has a new show, The Big Fat Truth, where he talks to former contestants to find out why they regained the weight

On The Biggest Loser, contestants successfully shed hundreds of pounds with intense dieting and exercise, but when they returned to their normal lives, many quickly regained the weight. Now, the show’s former executive producer, J.D. Roth, wants to figure out why on his new series, The Big Fat Truth.

Roth is bringing back six former contestants — including Ryan Benson, who won the first season of the show — who collectively lost 630 lbs. on The Biggest Loser, but then regained the weight and more.

The show comes after a study, profiled in The New York Times, found that the diet tactics on The Biggest Loser may have permanently damaged the contestants’ metabolisms, to the point where they are physically unable to keep the weight off.

“They started the biggest loser unfit, unhealthy and unhappy. Then, they finished the Biggest Loser hopeful, skinny, fit and ready to take on the world. But somewhere along the way, their old habits crept back in. And unfortunately, so did the pounds,” Roth says in this exclusive clip from the show, which premieres June 13 on Z Living network.

The New York Times published an article telling everyone that, ‘You can’t get away from a basic biological reality … as long as you are below your initial weight, your body is going to try to get you back.’ Could this really be true? How do you get lucky enough to get a lottery ticket to be on the Biggest Loser, lose all the weight, end up on the cover of People magazine, and then gain it all back?” Roth asks. “So is it your metabolism? Or is it your choices?”

In the first episode of The Big Fat Truth, Roth will work with the six former contestants for 90 days, to help them lose weight again. He’ll then work with other people — teachers, type 2 diabetics, nurses and more — during the rest of the series.

“The Big Fat Truth focuses on revitalizing our participants’ diets and mindsets, and within the first 10 days alone not only did we see considerable weight loss, but also significant decreases in insulin levels and bad cholesterol, among other positive changes,” Roth says. “This series is proof that the mind is the gateway to transforming the body.”

The Big Fat Truth airs Tuesdays at 8 pm ET on Z Living, beginning June 13.