Earlier quoted context omitted.
There's no breaking of the laws of physics involved here. Firstly you are still losing mass in this scenerio - but it is muscle tissue, not fat. Secondly, lower resting metabolic rate manifests itself in forms such as lower body temperature, or general lethargy, so you are burning fewer calories just for maintenance. Your body is a survival machine. If it thinks you are under threat of starvation, it will prioritize…
I read the first article listed on t-nation.com and it starts up with this poignant observation about olympic swimmers: "I'm sorry but these dudes look like AIDS patients. Would it kill you to at least get a tan and not remind the world of the Holocaust? And could you butch up the sport a little bit? Because deep down I know the male divers I just saw are in shower right now, naked, loofahing each other's taut athlet…
If you are specifically trying to lose weight, limiting calories is key, but you must eat plenty before and after these madman workouts and then don't eat as much on non-workout days. Just be sure to eat healthy stuff with a good ratio of macro nutrients. If you don't, the training will be more difficult and less effective.
Luckily, your body should be pretty good at telling you when it's hungry. Don't fight it (much). Diet and exercise info is all over the map, but the basics I have mentioned here are more or less undisputed.