I also spent 4 nights inside a sealed metabolic chamber. Every calorie in and out is measured (I'll spare you the scatalogical details). The chamber measures how much CO2 a person exhales, and these numbers together can measure metabolic rate. The chamber was loud - lots of fans - and I didn't get much sleep. Here's my arm sticking out of the chamber for blood work, with my friend Andreas filming for German television. 11/