I didn't watch the programme because I avoid anything that involves "Eating as much as you possibly can" as it usually involves vomit in the end... I've been traumatised by Jackass you see...
Anyhoo - I suppose the concept that some people put weight on more easily than others is slightly interesting, but only slightly so really.
The basics are these. If you ingest
n calories a day, your body will absorb somewhat less than
n for the purposes of energy. The efficiency of this is probably mostly genetic - ie, you can't bloody change it, so why worry about it?
Then - if you burn
x calories in activity - some, all or more than
n will be consumed. Because of the Laws of Thermodynamics:
If
x >
n -> The balance must be drawn from reserves. Has to. There's no chuffin way anything else can happen. So you will lose weight. If you do it properly (eg -
This way) then most of the difference will come from stored Fat. If you do it improperly (eg
This way) then the difference will come more from burning muscle, which will lower your metabolic rate and make it harder and harder to achieve
x >
n.
Sadly, the unwashed masses find this really hard to either comprehend, or achieve. Hence the desperate search for Diet Pills, Fad Diets and TV Programmes about why some people can eat three Christmas puddings an hour and not put on weight.