RTE's Kathryn Thomas said she would never take part in Operation Transformation as a leader - because the show can take over people's lives.
Thomas, who presents the successful television show, said much of each leader's day is filmed and scrutinised and she wouldn't do it "if you paid me".
"They are really putting themselves out there, walking onto a scales every week with it all hanging out," she told TV Now magazine.
"They have a camera in their house for 12 hours a day. Their family is affected, their children are affected, there are over 100,000 people talking about them on Facebook. The John Murray show is there. I'm there and it's a massive intrusion for them."
The host added that the leaders, who undertake an eight-week weight loss programme, can often be on the receiving end of a verbal tirade from the show's panel of health experts.
"They have to point out the shortcomings of the leaders," Kathryn said.
"You want everyone to step up to the mark, and the people the nation are putting their trust in to take it seriously."
Thomas, who also presents The Voice of Ireland, said she is also preparing herself for her own fitness challenge, as she's hoping to take on this year's Dublin Marathon.
"I've started training for the Dublin Marathon, so I'm our doing two long runs in the week.
"I stay quite clean in my eating, but I definitely treat myself at the weekend. I also try not to eat bread and potatoes. I try to eat more complex carbs like brown rice and sweet potatoes."