Short sleep duration increases energy intakes but does not change energy expenditure in normal-weight individuals.

BACKGROUND Evidence suggests a relation between short sleep duration and obesity. OBJECTIVE We assessed energy balance during periods of short and habitual sleep in normal-weight men and women. DESIGN Fifteen men and 15 women aged 30-49 y with a body mass index (in kg/m(2)) of 22-26, who regularly slept 7-9 h/night, were recruited to participate in this crossover inpatient study. All participants were studied under short (4 h/night) and habitual (9 h/night) sleep conditions, in random order, for 5 nights each. Food intake was measured on day 5, and energy expenditure was measured with the doubly labeled water method over each period. RESULTS Participants consumed more energy on day 5 during short sleep (2813.6 ± 593.0 kcal) than during habitual sleep (2517.7 ± 593.0 kcal; P = 0.023). This effect was mostly due to increased consumption of fat (20.7 ± 37.4 g; P = 0.01), notably saturated fat (8.7 ± 20.4 g; P = 0.038), during short sleep. Resting metabolic rate (short sleep: 1455.4 ± 129.0 kcal/d; habitual sleep: 1486.5 ± 129.5 kcal/d; P = 0.136) and total energy expenditure (short sleep: 2589.2 ± 526.5 kcal/d; habitual sleep: 2611.1 ± 529.0 kcal/d; P = 0.832) did not differ significantly between sleep phases. CONCLUSIONS Our data show that a reduction in sleep increases energy and fat intakes, which may explain the associations observed between sleep and obesity. If sustained, as observed, and not compensated by increased energy expenditure, the dietary intakes of individuals undergoing short sleep predispose to obesity. This trial is registered at clinicaltrials.gov as NCT00935402.