People that achieve massive weight loss often pile most of their weight back on again according to a new study. The reason why is that their bodies are fighting against them. 

Researchers came to this conclusion after analysing the 14 contestants from season 8 of the US reality series The Biggest Loser. In the six years since the show aired, 13 of the contestants have regained most if not all of the weight they lost. 

Danny Cahill, the series winner, lost 239lbs (just over 17st) from his 430lbs frame (30st 7lbs) during the seven months on the show He has since gained back 100lbs (7st). Dina Mercado, who weighed 248lbs (17st 7lbs) before the show, dropped to 173.5lbs (12st 3lbs) by the final, but now weighs 205.9lbs (14st 7lbs).

The reason behind the weight gain is called the 'metabolic adaption' according to scientists. People who lose weight often have a slower metabolism when their diet ends. Which was the case for all of The Biggest Loser contestants. So that didn't surprise scientists. 

What did surprise them is that six years on, their metabolic rate still hadn't recovered. In fact, in some cases, they'd even gotten slower. Meaning it was so much easier to start piling the weight back on again. 

‘It is frightening and amazing,’ Dr. Hall, an expert on metabolism told the New York Times. ‘I am just blown away.’

Of course that doesn't mean people can't and don't keep the weight off. There are a lot of other factors at work, whether biological or environmental. It's also worth noting that the contestants no longer had access to nutritionists or trainers once their stint on the show was complete. 

So although it's not impossible to keep the weight off once you go through dramatic weight loss it is scary to see that our bodies can be fighting against us afterwards. 

‘Long-term weight loss requires vigilant combat against persistent metabolic adaptation that acts to proportionally counter ongoing efforts to reduce body weight,’ the study concluded.