EFFECT OF PHYSICAL-TRAINING ON THERMOGENIC RESPONSES TO COLD AND EPHEDRINE IN OBESITY

The metabolic response to two tests: ephedrine and cooling in water at 15-degrees, was measured in eight obese and 13 normal weight persons matched for age and body height. The increase in heat production cause d by ephedrine was significantly lower in the obese subjects than in t he normal weight subjects. Also a 0.3-degrees-C degree fall in tympani c temperature during cold exposure induced a significantly smaller inc rease in energy expenditure and a reduced plasma noradrenaline respons e in the obese subjects. Six obese and six normal weight persons perfo rmed aerobic bicycle training for five weeks, and the tests were repea ted. Bicycle ergometer training for one hour per day (heart rate 140-1 60 bpm) for five weeks increased the maximal oxygen uptake by 13% and 12% (P < 0.05) in the obese and the normal weight subjects, respective ly. After training, the responses of the obese to ephedrine tended to increase, whereas no significant improvement in their cold-induced the rmogenesis was found. The study shows that obese subjects have a decre ased thermogenic response to sympathomimetic stimulation and to cold e xposure, which was only slightly improved by endurance training.