Figure 1. Study protocol.

Black boxes represent scheduled sleep opportunities and white boxes represent scheduled wakefulness. Breakfast, lunch, dinner and a snack are denoted by B, L, D and S, respectively. Relative clock hour is on the abscissa and day of study is on the ordinate. Day 1 consisted of a habituation and sleep disorders screening night. Day 2 (baseline) consisted of 16 h of wakefulness and 8 h baseline sleep opportunity. Day 3 (sleep deprivation) consisted of 24 h of sleep deprivation. Day 4 (recovery) consisted of the remaining hours awake 25–40 h of sleep deprivation and 8 h recovery sleep. Energy expenditure was measured during days 2, 3 and 4.