Postprandial thermogenesis and substrate oxidation are unaffected by sleep restriction

Abstract

Background/objectives: The extent to which alterations in energy expenditure (EE) in response to sleep restriction contribute to the short sleep-obesity relationship is not clearly defined. Short sleep may induce changes in resting metabolic rate (RMR), thermic effect of food (TEF) and postprandial substrate oxidation.

Subjects/methods: Ten females (age and body mass index: 22-43 years and 23.4-28 kg m(-2)) completed a randomized, crossover study assessing the effects of short (4 h per night) and habitual (8 h per night) sleep duration on fasting and postprandial RMR and respiratory quotient (RQ). Measurements were taken after three nights using whole-room indirect calorimetry. The TEF was assessed over a 6-h period following consumption of a high-fat liquid meal.

Results: Short versus habitual sleep did not affect RMR (1.01±0.05 and 0.97±0.04 kcal min(-1); P=0.23). Fasting RQ was significantly lower after short versus habitual sleep (0.84±0.01 and 0.88±0.01; P=0.028). Postprandial EE (short: 1.13±0.04 and habitual: 1.10±0.04, P=0.09) and RQ (short: 0.88±0.01 and habitual: 0.88±0.01, P=0.50) after the high-fat meal were not different between conditions. TEF was similar between conditions (0.24±0.02 kcal min(-1) in both; P=0.98), as was the ~6-h incremental area under the curve (1.16±0.10 and 1.17±0.09 kcal min(-1) × 356 min after short and habitual sleep, respectively; P=0.92).

Conclusions: Current findings observed in non-obese healthy premenopausal women do not support the hypothesis that alterations in TEF and postprandial substrate oxidation are major contributors to the higher rate of obesity observed in short sleepers. In exploring a role of sleep duration on EE, research should focus on potential alterations in physical activity to explain the increased obesity risk in short sleepers.

Figures

Figure 1

Illustration of the 4-d randomized, crossover research design. In-lab sleep conditions included short sleep duration (4 h/night time in bed, from 0100-0500 h) and habitual sleep duration (8 h/night time in bed, from 2300-0700 h) and. Black bars represent sleep opportunities. Grey bars represent time spent in the small, whole-room indirect calorimeter for measures of energy expenditure in a semi-recumbent position. RMR, resting metabolic rate as measured in the fasting state from 0730-0815 h. TEF, thermic effect of food from 0815-1420 h, as calculated by subtracting RMR from values of postprandial energy expenditure following a high-fat breakfast shake served at 0815 h. B, breakfast; L, lunch; S, snack; D, dinner.

Figure 2

Energy expenditure (EE) and respiratory quotient (RQ) in the fasting state from 0745-0815 h after 3 nights of habitual (8 h/night) and short (4 h/night) sleep duration measured with whole-room indirect calorimetry. Two-way ANOVA for repeated measures demonstrated that EE (illustrated with triangles) showed a significant sleep condition x time interaction (p=0.03), but no main effect of sleep condition (p=0.23) or time (p=0.96) was seen. Two-way ANOVA for repeated measures demonstrated that RQ (illustrated with circles) showed a significant main effect of sleep condition (p=0.03), but no main effect of time (p=1.00) and no sleep condition x time interaction (p=0.76) was seen. Open symbols represent the short sleep condition and filled symbols represent the habitual sleep condition. * denotes significant difference between short and habitual sleep duration conditions. Plotted values are mean ± SEM. n = 10.

Figure 3

Thermic effect of food (TEF) in response to a high-fat breakfast shake after 3 nights of habitual (8 h/night) and short (4 h/night) sleep duration measured with whole-room indirect calorimetry. TEF showed a significant main effect of time (p