Fig. 1.

Study schematic. Black bars represent time in bed (TIB). For at least 1 wk before admission, participants maintained a 10-h TIB routine from 22:00–08:00. After admission, participants were kept on the same 10-h TIB schedule for 3 additional nights (baseline condition; TIB: 22:00–08:00); then sleep was curtailed to 5 h/night, maintaining nocturnal midpoint, for 5 nights (sleep restriction condition; TIB: 00:30–5:30). Finally, participants resumed the 10-h TIB schedule for 2 nights (recovery condition; TIB: 22:00–08:00). An intravenous glucose tolerance test (IVGTT) was performed on the final day of each condition (days 4, 9, and 11).