A new study has revealed that losing weight actually gets harder, not easier, after appearing on The Biggest Loser.

Noticing that a large number of contestants on The Biggest Loser struggle to keep the weight off once they leave the house, scientist Kevin Hall decided to figure out why that was.

Hall, an expert on metabolism at the US National Institute of Diabetes and Digestive and Kidney Diseases, which is part of the National Institutes of Health, studied contestants from the eighth season of the US version of The Biggest Loser for six years after the show ended.

That season of the show was won by Danny Cahill, who shed a stunning 108 kilograms in seven months. But he’s piled 45 of those kilos back on since then, and he’s hardly unique — 13 of the 14 contestants regained weight after leaving the show.

Danny Cahill

Danny Cahill

Why? Because the body fights like hell to keep weight on.

In a result that has massive implications for anyone looking to lose weight, the researchers found that anyone who deliberately loses weight — even if they start at a normal weight, or underweight — will have a slower metabolism by the time their diet ends.

So how does that work, exactly?

When the contestants started out on The Biggest Loser, they had normal metabolisms for their weight, but by the time the show ended, their metabolisms had slowed down immensely, so their bodies weren’t burning enough calories to keep the weight off.

So far, these results are not necessarily shocking. But here’s what really surprised the researchers — as the years went on and the contestants started regaining the weight they’d lost on the show, their metabolisms didn’t speed back up to match.

In fact, their metabolisms got even slower.

Cahill’s metabolism has slowed so much, in fact, that just to maintain his current weight (which is still, keep in mind, 45 kilos heavier than he was when he won The Biggest Loser), he can only eat 800 calories a day.

If he doesn’t stick to that number, his weight will explode, a bit like the bus in Speed.

To give those 800 calories some context, the average man at Cahill’s age can eat 1800 calories a day while maintaining a healthy weight.

So what does this all mean? Well, it means that if you’ve tried to lose weight only to find the pounds piling back on in a hurry, it’s not necessarily your fault — it’s science, as you’re up against a metabolism that is trying to get you back to your old weight.

Essentially, you’re fighting your own biology.

Or, as Biggest Loser contestant Rudy Pauls told The New York Times, which published an extensive report on the results of the study: “The Biggest Loser did change my life, but not in a way that most would think. It opened my eyes to the fact that obesity is not simply a food addiction. It is a disability of a malfunctioning metabolic system.”

The study’s findings will be published in the Obesity journal this month.