Purpose: To determine the effect of innate activity level and running wheel access on food consumption in high-active (SWR/J) low-active (DBA/2J) mice.
Methods: Two strains of inbred mice were used in this study owing to their high activity level (SWR/J) and low activity level (DBA/2J). Mice were housed in individual cages, and half of the mice in each strain had free access to running wheels in their cages, whereas the other half received no running wheel. All mice consumed standard chow and water ad libitum for 13 wk during the study period. Running wheel activity (daily), food consumption (biweekly), and body mass (weekly) were recorded.
Results: SWR/J runners consumed more food (6.0 ± 0.4 g·d−1) than SWR/J nonrunners (4.7 ± 0.2 g·d−1, P = 0.03), DBA/2J runners (4.6 ± 0.2 g·d−1, P = 0.02), and DBA/2J nonrunners (4.2 ± 0.2 g·d−1, P = 0.006). SWR/J nonrunners consumed more food than DBA/2J nonrunners (P = 0.03). Average daily distance and duration were significantly greater for the SWR/J runners (6.4 ± 0.7 km·d−1 and 333.6 ± 40.5 min·d−1, respectively) compared with those for the DBA/2J runners (1.6 ± 0.4 km·d−1 and 91.3 ± 23.0 min·d−1, respectively). There was a significant correlation between food consumption and distance (r = 0.74, P < 0.001), duration (r = 0.68, P < 0.001), and speed (r = 0.58, P < 0.001), respectively, in all mice. However, when considering the individuals strains, the relationship between running wheel activity and food consumption was only statistically significant for the SWR/J mice.
Conclusions: Higher running wheel activity in mice was associated with increased food consumption in the SWR/J mice but not in the DBA/2J mice. In DBA/2J mice, addition of a running wheel did not result in increased food consumption, suggesting that energy expenditure of nonwheel cage activity in the control DBA/2J mice was similar to the energy expenditure of the wheel activity because body mass was similar between the two groups.