Effects of isocaloric high-fat diet on energy metabolism and endurance exercise capacity in SD rats

To investigate the effects of a 45% high-fat diet (HFD) with isocaloric intake on energy metabolism and endurance exercise capacity in SD rats.

Twenty-four male SD rats were randomly divided into normal chow diet group (CON), HFD group, normal chow diet+exercise training group (CONT), and HFD+exercise training group (HFDT). The CON and CONT groups received normal chow diet, while the HFD and HFDT groups received a 45% high-fat diet with isocaloric intake. The HFDT and CONT groups underwent an endurance training of moderate-intensity running for 6 weeks. Body weight, fat mass, and lean mass were measured weekly. Energy expenditure and basal metabolic rate during rest and exercise states were measured using Pheno Master/Calo Treadmill system. Blood glucose, lipids, and creatine kinase levels were detected after the exhaustion test.

In 6 weeks after intervention, the endurance exercise capacity was significantly enhanced in the HFDT group than the CONT group (P<0.05). There were no obvious differences in body weight and body composition among the groups under isoenergetic feeding conditions. At rest, no statistical differences were observed in total energy expenditure and basal metabolic rate among the groups. However, prior to the 4th week, the CON group primarily metabolized carbohydrates while the HFD group primarily metabolized fats. But the carbohydrate metabolism was decreased and then increased, and the substrate metabolism rates eventually reached similar levels between the 2 groups on the 5th to 6th week. The HFDT group primarily metabolized fats while the CONT group primarily metabolized carbohydrates, with significant differences persisting after 6 weeks of training (P<0.05). HFD led to elevated levels of serum cholesterol, triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C), but, endurance training resulted in decreased lipid levels in the HFDT group, accompanied by an increase in β-hydroxybutyrate (βHB) level (P<0.05). Isoenergetic diets had no significant differences in their effects on liver and kidney function or muscle damage indicators.

An isoenergetic HFD can improve fat utilization ability and extend endurance exercise time in rats without altering body composition or affecting liver and kidney function.