FAT LOSS IN THE COLD - CONTROLLED-STUDY

A simple crossover design tested the specificity of fat loss induced by exercise in the cold. Fifteen middle-aged, moderately obese males exercised 2.5 h/day for 2 wk, separated by an intervening (recovery) week. For 1 wk, the climatic chamber was maintained at -40°C (still air, full arctic clothing), with ambient temperatures for the alternate week. A total daily energy expenditure of about 13 MJ was estimated from diary records of activity, the tables of Durnin and Passmore, and Kofranyi-Michaelis measurements of oxygen consumption for subjects in the chamber. Comparison with diary records of food consumption showed a small energy deficit (~2.9 MJ/day) over both warm and cold exposures. Cold exposure led to a reduction of skinfold thicknesses and an increase of body density (underwater weighing), with a loss of body fat (2.3 kg from skinfolds, 0.8 kg from underwater weighing) and a 1.5-kg increase of lean body mass. However, no significant changes of body composition occurred with compatible exercise under temperate conditions. Core temperatures were well maintained in the cold environment, but skin temperatures were 10°C lower than under ambient conditions. Mean skin temperature in the cold was positively correlated with fat loss. The observed fat loss in the cold can be explained by new protein synthesis, ketosis, and a small energy deficit.