Loss of body weight and fat during exercise in a cold chamber.

Ten men spent one week in a cold climatic facility performing a simulated arctic military exercise demanding an energy expenditure of 13-16 MJ-day-1. Although the ration pack was adequate, extensive plate wastage led to a negative energy balance of 2.2 MJ-day-1. Fluid intake was also insufficient, with a 3.25% decrease of body weight, and a 9.7% decrease in skin thickness over the cold exposure. Extensive fat mobilization was indicated by a decrease of skinfold thicknesses, an increase of body density, and associated ketonuria and glycosuria. The fat breakdown far exceeded the calculated energy deficit, and it is postulated that much of the "surplus" energy was required for synthesis of additional muscle protein. In the arctic environment, both energy and fluid balances are better maintained because there are few distraction from the simple pleasure of preparing and eating meals.