Worried trainers Jillian Michaels and Michelle Bridges have spoken out about their fears for contestants on The Biggest Loser, with Jillian claiming she has no control over their demanding workouts and is scared the unfit competitors could keel over.

The entrants’ obesity and lack of fitness before they start on the show mean they risk a heart attack or injury from the moment they set foot in the Loser headquarters, where their diets are drastically changed and strict workouts begin immediately.

“The contestants keep getting bigger and bigger,” Jillian says. “As the trainers, we have no say over the challenges. We worry about them.”

The famous American fitness fanatic has risked her spot on the top-rating show by speaking out about the drama we never see on screen, admitting ice-packs are often needed to tend over-extended muscles.

“For every 10 minutes we’re on the show, there are a hundred hours of training you don’t see … the stretching, the icing.”

Australian trainer Michelle Bridges agrees the competition is tough on contestants.

“I have many sleepless nights concerned about their welfare, concerned about their health and concerned about their headspace.

“I would definitely say they take it to the edge.”

Teams of medics, dietitians and other personnel are on hand 24 hours a day to monitor participants.

“We have got them exercising like they have never exercised before,” Michelle says.

“They do push the boundaries, but what comes out of that is the contestants looking back on what they have done and going, ‘I had no idea I could even do that’.”