Unaltered regulatory thermogenic response to dietary signals in exercise-trained rats.

Thermogenic response to ingestion of high-fat diet was investigated in four groups of male rats, two groups being exercise trained and two remaining sedentary. One sedentary and one trained group each received a high-fat dietary supplement in addition to the stock diet. After 35 days, body energy and protein and fat contents were determined. Results indicate that exercise reduced metabolizable energy (ME) intake by 9 and 18% in stock- and high-fat-fed trained rats, respectively. Compared with stock-fed rats, ME intake was elevated 31 and 18% in sedentary and trained high-fat-fed rats, respectively. Exercise also affected energy gains; trained rats deposited almost 60% less energy than controls. Exercise largely decreased both fat and protein contents of rats, whereas the high-fat supplement enhanced fat deposition. Energy expenditure, excluding exercise cost, was calculated on a mass-independent basis and was revealed to be similar in appropriately matched (diet) trained and sedentary rats. High-fat feeding induced increases in expenditure assumed to be due to enhanced brown adipose tissue (BAT) regulatory diet-induced thermogenesis. Conversely, exercise did not affect further the regulatory thermogenic response of BAT to stimuli originating from high-fat diet. Excluding physical activity, energy expenditure components in sum (expressed mass independently), in high-fat- and stock-fed rats, appear unaltered by exercise training.