Insufficient sleep undermines dietary efforts to reduce adiposity

Abstract

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.

Figure 1. Experimental protocol

Schematic diagram of the study protocol. TIB: assigned time-in-bed (hours per night); DXA: measurement of body composition using dual X-ray absorptiometry; TEE: measurement of total energy expenditure using doubly labeled water; RMR and RQ: measurement of resting metabolic rate and respiratory quotient by indirect calorimetry.

Figure 2. Changes in body weight and composition

Box plots of the weight loss and its composition during the 8.5-h (open circles) and 5.5-h (solid circles) time-in-bed condition (n=10). Asterisk: significant difference in loss of fat (P=0.043) and fat-free body mass (P=0.002) between the two sleep conditions controlling for study period (initial vs. crossover) and pre-treatment body composition.

Figure 3. Substrate utilization

Mean (±SD) respiratory quotient (RQ) under fasting conditions (time 0) and during four consecutive 1-h intervals after breakfast at the end of the 8.5-h (open triangles) and 5.5-h (solid circles) time-in-bed condition (n=10). Asterisk: significant difference in fasting (P=0.042) and 4-h postprandial RQ (P=0.038) controlling for study period and body composition at the end of each intervention.

APPENDIX Figure I. Selected metabolic hormone profiles

A: Mean ± SE (n=10) 24-hour profiles of serum leptin at the beginning (open circles) and the end (solid circles) of the 8.8-h time-in-bed condition (TIB-8.5h, left panels) and 5.5-h time-in-bed condition (TIB-5.5h, right panels) condition; B: Mean ± SE (n=10) 24-hour profiles of serum acylated ghrelin at the beginning (open circles) and the end (solid circles) of the TIB-8.5h (left panels) and TIB-5.5h (right panels) condition. Times of controlled identical calorie intake are marked with vertical dotted bars.