mPer2−/− mice have attenuated feeding rhythm. A, The amount of regular diet (regular chow diet) consumed during light and dark periods (n = 5–6 per genotype). Results are mean ± sem. Single-factor ANOVA between mPer2+/+ and mPer2−/− mice was P = 0.008 and F = 10.1 (**) during light period, and P = 0.016 and F = 7.7 (*) during dark period. Two-way ANOVA (genotype × period): P = 0.0003, F = 17.4 for interaction; P = 0.95, F = 0.004 for genotype; and P < 0.0001, F = 50 for period. B, The amount of HFD consumed during light and dark periods (n = 13–17 per genotype). Results are mean ± sem. Single-factor ANOVA between mPer2+/+ and mPer2−/− mice during the light period: P = 3.3e-08 and F = 58 (*****). There was no difference in the dark period. Two-way ANOVA (genotype × period): P < 0.0001, F = 26.2 for interaction; P = 0.0004, F = 14.5 for genotype; and P = 0.0005, F = 13.8 for period. C, Twenty-four hour food intake of regular diet and HFD. Single-factor ANOVA between mPer2+/+ and mPer2−/− mice on HFD: P < 0.0001, F = 19.4 (***). Two-way ANOVA (genotype × diet): P < 0.001, F = 8.6 for interaction; P = 0.0002, F = 15.0 for genotype; and P = 0.04, F = 2.9 for food.