Experimental sleep curtailment causes wake-dependent increases in 24-h energy expenditure as measured by whole-room indirect calorimetry

Abstract

Background: Epidemiologic evidence has shown a link between short sleep and obesity. Clinical studies suggest a role of increased energy intake in this relation, whereas the contributions of energy expenditure (EE) and substrate utilization are less clearly defined.

Objective: Our aim was to investigate the effects of sleep curtailment on 24-h EE and respiratory quotient (RQ) by using whole-room indirect calorimetry under fixed-meal conditions.

Design: Ten females aged 22-43 y with a BMI (in kg/m²) of 23.4-27.5 completed a randomized, crossover study. Participants were studied under short- (4 h/night) and habitual- (8 h/night) sleep conditions for 3 d, with a 4-wk washout period between visits. Standardized weight-maintenance meals were served at 0800, 1200, and 1900 with a snack at 1600. Measures included EE and RQ during the sleep episode on day 2 and continuously over 23 h on day 3.

Results: Short compared with habitual sleep resulted in significantly higher (± SEM) 24-h EE (1914.0 ± 62.4 compared with 1822.1 ± 43.8 kcal; P = 0.012). EE during the scheduled sleep episode (0100-0500 and 2300-0700 in short- and habitual-sleep conditions, respectively) and across the waking episode (0800-2300) were unaffected by sleep restriction. RQ was unaffected by sleep restriction.

Conclusions: Short compared with habitual sleep is associated with an increased 24-h EE of ~92 kcal (~5%)--lower than the increased energy intake observed in prior sleep-curtailment studies. This finding supports the hypothesis that short sleep may predispose to weight gain as a result of an increase in energy intake that is beyond the modest energy costs associated with prolonged nocturnal wakefulness.

Trial registration: ClinicalTrials.gov NCT01751581.

Figures

FIGURE 1.

Illustration of laboratory procedures. Participants entered the laboratory for a 4-d inpatient stay in a randomized crossover design. Experimental sleep conditions included habitual sleep duration (8 h/night sleep opportunity, from 2300 to 0700) and short sleep duration (4 h/night sleep opportunity, from 0100 to 0500). Solid black bars represent acclimatization sleep episodes occurring in the metabolic chamber without the door sealed. White hatched bars represent time spent awake inside the metabolic chamber. Black hatched bars represent time spent in bed inside the metabolic chamber. B, breakfast; D, dinner; L, lunch; S, snack.

FIGURE 2.

Mean (± SEM) energy expenditure throughout the 23-h metabolic chamber in the laboratory on day 3 during the short- and habitual-sleep duration conditions. Two-way within-subjects ANOVAs for repeated measures (factors: sleep condition and time) showed a significant sleep condition × time interaction (P < 0.001). *P < 0.05 (simple main-effects tests). Open circles represent the short-sleep condition (0100–0500), and filled circles represent the habitual-sleep condition (2300–0700). Values on the x axis are for the preceding hour. Black bars represent the sleep opportunity.

FIGURE 3.

Mean (±SEM) energy expenditure during exercise sessions on laboratory day 3 during the short- and habitual-sleep duration conditions. Three-way within-subjects ANOVA for repeated measures (factors: sleep condition, exercise session, and time) showed a significant session × time interaction (P < 0.0001), with increased EE in the afternoon bicycling session (1500–1515) compared with the evening bicycling session (2030–2045) at minutes 1–6 of the 15-min exercise session. Differences between sessions at given time points are indicated by lowercase letters: a1 > b1, a2 > b2, a3 > b3, a4 > b4, a5 > b5, and a6 > b6 (P ≤ 0.05; simple main-effects tests). Open circles represent the short-sleep condition (0100–0500), and filled circles represent the habitual-sleep condition (2300–0700). EE, energy expenditure.