In America the TV show The Biggest Loser has proved a ratings smash, with thousands tuning in to see the contestants get put through a gruelling weight loss program in an effort to win the $250,000 prize and of course get healthy.

However there has been increasing criticism of the methods used to get the contestants down to a healthy weight and medical experts have expressed serious concerns that the participant’s health is being put at risk in order to make the trials – and results – more extreme.

The winner from 2005, Ryan Benson, has admitted that while following the rapid weight loss plan at one point he was urinating blood and became dehydrated. During the current season, 2 of the contestants ended up being hospitalised during the first episode, with one having to be airlifted to hospital after collapsing during a one-mile race due to heat stroke.

Other contestants have said they were so eager to demonstrate rapid weight loss before weigh-ins that they would drink as little as possible in the 24 hours before getting on the scales.

Dr. Charles Burant, Professor of Internal Medicine at the University of Michigan and director of the Michigan Metabolomics and Obesity Centre, told the New York Times that he was ‘waiting for the first person to have a heart attack’. Doctors generally advise dieters to aim for weight loss of no more than 2 pounds a week, as rapid weight loss can cause the heart muscle to weaken, the heart to beat irregularly and potassium and electrolyte levels to become dangerously low.

Dr. Durant added, “I think the show is so exploitative. They are taking poor people who have severe weight problems whose real focus is trying to win the quarter-million dollars.”

Since the show began, contestants entering the program have become steadily heavier, with the last two seasons featuring people weighing 454 and 476 pounds. Contestants are put through a rigorous weight loss program, with daily hikes, runs and cardiovascular exercise and a low-calorie diet. While the exercise regime is extreme by any standards, the weight of the contestants means that the routines are especially gruelling.

One of the show’s trainers has acknowledged that some of their practices have been ill-judged. Dr. Huizenga, speaking of the mile-long race that resulted in hospitalisation, said, “If we had to do it over, we wouldn’t do it. It was an unexpected complication and we going to do better…(and) that challenge has changed a lot of the way we do things. “

JD Roth a producer on the show and the creator of its format, defended the challenging nature of the program, arguing, “It needs to be extreme in my opinion.”