EXERCISE-TRAINING REDUCES BAT THERMOGENESIS IN RATS

In the energy balance equation, physical activity represents one compo nent of energy expenditure. From various studies it appears that exerc ise-training does not affect clearly thermogenesis which depends on br own adipose tissue (BAT) activity. In the present work we examine how exercise-training can influence food intake and body weight regulation in relation to BAT thermogenesis. The proton conductance of the uncou pling protein of BAT was examined in male adult Wistar trained 2 h/day for 20 days and compared to that of sedentary (2 h of fasting instead of exercise) or control animals. All animals were provided with separ ate sources of the 3 macronutrients (protein, fat and carbohydrate) co ntaining an identical percentage of vitamins, salt mixture and cellulo se powder. At the end of training, rats were placed at 5 degrees C dur ing 10 days, then during 4 days at 28 degrees C. This condition has be en demonstrated to favour and amplify BAT responsiveness to moderate m odifications of stimulation. The body weight of trained rats became si gnificantly lower than that of the control and sedentary rats and this difference persisted all throughout the experiment. When placed at 5 degrees C, all rats increased their total ingestion: control rats enha nced fat intake, while sedentary and trained rats enhanced carbohydrat e ingestion. When placed at 28 degrees C, all rats had identical total energy and that of the 3 items intakes. BAT proton conductance was ab out 40% lower in the trained compared with the sedentary plus the cont rol rats. This indicated a lower BAT thermogenic activity in the train ed animals. It could be concluded that exercise-training in rats induc es negative energy balance; the reduced BAT activity could restrain we ight loss and overeating.