Tim Worstall is probably right.
I devised my own theoretical weight-loss plan some time ago. The only problem was that I could find no way to market it. It's based on a trivial bit of physics.
Let's start with some assumptions or background:
* Let's assume the core temperature of the body is 37 degrees centigrade
* Remember that the specific heat capacity of water is about 4.2 Joules per kilogram kelvin. That's almost precisely 1 calorie. (Hmmm... strange that....).
This means that if you drink a litre of ice-cold water, you will burn off 37 calories by the simple process of warming it up inside your own body.
Fantastic! You can burn off about a hundred calories simply by drinking three litres of icewater.
I thought I had stumbled upon the germ of a truly great business idea until I remembered that humans tend to measure energy in kilocalories. You'd have to drink over 81,000 litres of water to lose a pound. Oops....