Fig. 4.

The respiratory exchange ratio (RER; CO₂ produced/O₂ consumed) during the light (A) and dark cycles (B) in male (WT, C; PKU, E; time course over 24 h) and female (WT, D; PKU, F; time course over 24 h) mice fed CAS, AA, and GMP diets. Significant interaction of sex and diet was observed. Values are means + SE; nos. in parentheses indicate sample size. ^a,b,cMeans with different superscripted letters reflecting the significant interaction of sex and diet are significantly different (P < 0.05). During the dark cycle, there was a significant effect of genotype with higher RER in PKU vs. WT mice (P = 0.0380).