Effect of the detraining status on high-fat diet induced fat accumulation in the adipose tissue and liver in female rats

The purpose of the present study was to investigate the effects of a high-fat diet (HFD) in previously trained rats that have been detrained for different periods. Two groups of female rats were, first, either treadmill trained for 8 weeks or remained sedentary (Sed). Trained animals, thereafter, remained inactive for 4 weeks (Inact-4 weeks), while fed a standard diet, before being submitted to a high-fat diet (42% kcal of fat) for an additional 2 or 6 weeks. The order was reversed in a 3rd group in which rats were first kept sedentary for 4 weeks before being submitted to the same 8-week training program that ended with the initiation of the HFD (Inact-0 week). Fat accumulation in the mesenteric depot (P<0.05) and in the sum of 3 intra-abdominal (urogenital, retroperitoneal, and mesenteric; P=0.065) tissues in response to the HF feeding was higher in trained rats kept inactive for 4 weeks than in Sed and Inact-0 week animals. Liver triacylglycerol accumulation also showed a tendency to be higher (P<0.07) in Inact-4 weeks than in Inact-0 week rats. These changes were not associated with significant changes in fat cell diameter and number in the mesenteric adipose tissue. When rats in all groups were subdivided into obesity prone (OP) and obesity resistant (OR) on the basis of the change in body weight gain in response to the HFD, liver lipid infiltration was higher (P<0.01) in OP Inact-4 weeks rats than in all other groups. The present results indicate that previously trained rats that have been inactive for a while maintain higher body adiposity in response to a HFD than in freshly inactive and sedentary rats.