In young (panels A-D) and older subjects (panels E-H), mean profiles (± 95% C.I) are depicted for glucose (panels A, B, E, F) and insulin (panels C, D, G, H) responses to an identical, standardized breakfast (striped horizontal bar at time=0) under conditions of baseline sleep replete (≥10 h TIB/24 h [dashed black line]), history of prolonged sleep restriction combined with circadian disruption (5.6 h TIB/24 h [solid red line; left panels]), and following 9 days of stable circadian re-entrainment and recovery sleep (10 h TIB/24 h [solid grey line; right panels]). In each condition, breakfast was served at the same circadian temperature phase ± 4 h (0.7 h ± 1.8 h).