There are a lot of ways to get lean. I am not certain this is one of them. However, thumbing through The Four Hour Body by Tim Ferris, he made a case for why Michael Phelps supposedly burns 11,000 calories/day. By being in 80 degree water for 4-6 hours/day swimming, his body is under a thermal load trying to heat itself up. So if one can get the body really cold, where you shiver for hours, the body is burning mega calories trying to heat you up to the magical temp.
I figured it's worth a shot. Besides, whenever I see an icy stream, I wonder just how cold it really feels.
For the record. I shivered for three hours.
