The effects of short-term consumption of a Western diet on aerobic exercise performance in bank voles with inherently distinct metabolic rates.

Because obesity and related diseases are partly attributed to unrestricted consumption of a high-fat, high-sugar Western diet (WD), several studies have examined its adverse effects on health and physical fitness. However, short-term WD supplementation has received little attention. We asked whether such supplementation can improve the aerobic exercise performance of animals with inherently distinct aerobic capacity. We used bank voles [Clethrionomys (= Myodes) glareolus] from lines selected for high swim-induced aerobic metabolism (A) and unselected control lines (C). In a crossover design, we measured endurance running distance, aerobic capacity ( V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}{\mathrm{max}}}}$ ), peak speed (Vmax) and respiratory exchange ratio in 98 animals fed standard rodent diet (14.5 kJ/g) or WD (20.5 kJ/g; 48% from carbohydrates, including 28% from added sucrose, and 39% from fat) for 2 days before the trials. The V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}{\mathrm{max}}}}$ , Vmax and endurance distance were higher in A lines than in C lines. In A lines, endurance distance increased with Vmax but not with V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}{\mathrm{max}}}}$ , whereas in C lines it increased more with V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}{\mathrm{max}}}}$ than with Vmax. The WD treatment resulted in increased body mass (p = 0.006) and did not affect V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}{\mathrm{max}}}}$ (p = 0.4), but tended to decrease Vmax (p = 0.04), endurance distance (p = 0.099), mass loss during the trials (p = 0.008) and, in A lines only, the respiratory exchange ratio (p = 0.02). These results show that the selection experiment provides a model of genetically distinct aerobic athletes and non-athletes, in whom exercise performance appears to be limited by different mechanisms. Regardless of the genetic background, short-term WD supplementation does not improve aerobic exercise performance and reduces the effectiveness of exercise as a method of weight loss.