Energy balance and physical activity was assessed in female mice after 6 weeks of HF feeding, before the body weight of the null mice statistically diverged from the controls. (a) Energy expenditure, (b) respiratory quotient (RQ), (c) average meal size, (d) numbers of meals, (e) total food intake, (f) pedestrian distance, and (g) the mean pedestrian speed were presented. White bars for mmp9+/+ and black bars for mmp9−/−. N=5/genotype. *p<0.05 when compared to mmp9+/+ HF. †p=0.07 when compared to mmp9+/+ HF.