Differences in the major components of the body (fat, muscle and free fluid levels) between old (18–20 months) male and female (a–c) and adult (7–9 months) female (d–f) Hcrt KO and WT mice. Each bar represents the mean value + SEM. a = Significant difference between female WT (+/+) and female KO (−/−) mice, b = significant difference between female and male KO mice, c = significant difference between female and male WT mice, d = significant difference between male WT and KO mice, at the level of p < 0.05*, p < 0.01**.