Background: Sleep loss can modify energy intake and expenditure.

Objective: To determine whether sleep restriction attenuates the effect of a reduced-calorie diet on excess adiposity.

Design: Randomized, 2-period, 2-condition crossover study.

Setting: University clinical research center and sleep laboratory.

Patients: 10 overweight nonsmoking adults (3 women and 7 men) with a mean age of 41 years (SD, 5) and a mean body mass index of 27.4 kg/m² (SD, 2.0).

Intervention: 14 days of moderate caloric restriction with 8.5 or 5.5 hours of nighttime sleep opportunity.

Measurements: The primary measure was loss of fat and fat-free body mass. Secondary measures were changes in substrate utilization, energy expenditure, hunger, and 24-hour metabolic hormone concentrations.

Results: Sleep curtailment decreased the proportion of weight lost as fat by 55% (1.4 vs. 0.6 kg with 8.5 vs. 5.5 hours of sleep opportunity, respectively; P = 0.043) and increased the loss of fat-free body mass by 60% (1.5 vs. 2.4 kg; P = 0.002). This was accompanied by markers of enhanced neuroendocrine adaptation to caloric restriction, increased hunger, and a shift in relative substrate utilization toward oxidation of less fat.

Limitation: The nature of the study limited its duration and sample size.

Conclusion: The amount of human sleep contributes to the maintenance of fat-free body mass at times of decreased energy intake. Lack of sufficient sleep may compromise the efficacy of typical dietary interventions for weight loss and related metabolic risk reduction.

Primary funding source: National Institutes of Health.