Enhanced adipose tissue lipoprotein lipase activity in detrained rats: independent of changes in food intake.

Short-term detraining has been characterized by increased body mass and rapid body fat accretion. However, detraining has also been associated with increased food intake, especially in rats genetically predisposed to obesity. Thus, it has been difficult to separate refeeding effects from alterations resulting from the cessation of exercise training. In the present study, the in vitro activity of adipose tissue lipoprotein lipase (ATLPL) was measured in freely running wheel-trained rats and rats that had stopped training for 1, 2, or 3 days or 1 or 2 wk, respectively. Heparin-releasable ATLPL activity was measured at rest and after acute exhaustive exercise. Feeding efficiency (change in body mass/kJ ingested energy), fat pad mass, and adipocyte size were also measured. The rate of weight gain in 1- and 2-wk detrained rats was significantly higher than that of sedentary control or trained rats (P < 0.05). Feeding efficiency was also higher in 1-wk detrained rats than in all other groups (P < 0.005). However, food energy intake was not different between trained rats, 1- and 2-wk detrained rats, or sedentary control rats. ATLPL activity in all groups was highest after acute exhaustive exercise. ATLPL activity in 1-wk detrained rats was nearly threefold higher compared with that in trained rats (P < 0.005) and was not different from that of sedentary control rats. These results suggest that the cessation of exercise training causes an enhanced capacity for lipogenesis independent of changes in food energy intake or the acute effects of the last bout of exercise.