Figure 1.

a, b, Distance run (a), and body weight changes (b) over a 6 week period. Means ± SEM are plotted. a, Rats (n = 16) ran an average of 1028 ± 120 m the first week of the study, and showed a steady decrease over the course of the study with distances stabilizing ∼470 ± 67 m in weeks 5 and 6. b, Inset (starting body weights), A one-way ANOVA showed that there were no differences in body weight at the start of the study among the 3 groups: F_(2,31) = 0.87, p > 0.05; n = 8–16. Percentage body weight changes over 6 weeks, A repeated-measures ANOVA showed there was a significant main effect of physical activity (sedentary, locked, runners), F_(2,29) = 42.12, p < 0.0001; a significant main effect of time, F_(5,10) = 8.02, p < 0.0001; and a significant physical activity × time interaction, F_(10,145) = 7.90, p < 0.0001. Fisher's post hoc tests revealed that runners (n = 16) had lost significantly more weight than did both sedentary rats (n = 8) and those with a locked wheel (n = 8) beginning with the first week of the study and continuing on through the last (p < 0.0001, each week). Rats housed with a locked wheel also showed a weight reduction compared with sedentary rats, but these were only significant beginning on week 4 and continuing through week 6 (p < 0.01, each week). Sedentary rats gained an average of 0.55%, while rats housed with locked wheels lost an average of 1.73%, and runners lost an average of 5.52% of their starting weight.