Table 1.
Sleep and reduction in body weight and adiposity
| Baseline characteristics | TIB-8.5h | TIB-5.5h | Differencea | P |
| Body weight (kg) | 82.0 (11.2) | 80.5 (10.3) | −1.5 (2.1) | 0.057 |
| Body mass index (BMI, kg/m2) | 27.5 (2.2) | 27.1 (2.0) | −0.5 (0.7) | 0.069 |
| Body fat (kg) | 26.4 (6.4) | 25.0 (6.3) | −1.4 (1.6) | 0.022 |
| Fat-free body mass (kg) | 55.6 (11.5) | 55.5 (11.2) | −0.1 (0.7) | 0.84 |
| 14-day mean sleep parameters | TIB-8.5h | TIB-5.5h | Differencea | P |
| Total sleep time (h:min) | 7:25 (0:32) | 5:14 (0:06) | −2:11 (0:30) | <.001 |
| Sleep efficiency (%) | 87 (6) | 95 (2) | 8 (5) | 0.001 |
| Sleep onset latency (min) | 21 (9) | 7 (4) | −14 (6) | <.001 |
| Wake (min) | 66 (31) | 16 (5) | −50 (29) | <.001 |
| Stage 1 sleep (min) | 29 (10) | 12 (3) | −17 (9) | <.001 |
| Stage 2 sleep (min) | 264 (37) | 180 (42) | −84 (36) | <.001 |
| Slow wave sleep (stages 3+4; min) | 43 (28) | 46 (34) | 3 (24) | 0.66 |
| REM sleep (min) | 108 (22) | 76 (13) | −32 (16) | <.001 |
| End of treatment | TIB-8.5h | TIB-5.5h | B (95% CI) | P |
| Weight loss (kg) | 2.9 (1.4) | 3.0 (1.0) | 0.2 (−0.2, 0.7)b | 0.24 |
| Loss of fat-free mass (kg) | 1.5 (1.3) | 2.4 (1.4) | 1.0 (0.4, 1.5)b | 0.002 |
| Loss of fat (kg) | 1.4 (0.9) | 0.6 (0.6) | −0.7 (−1.4, −0.03)b | 0.043 |
| Fraction of weight loss as fat (%) | 56 (35) | 25 (24) | −31 (−49, −12)b | 0.004 |
| Fasting RQ | 0.80 (0.04) | 0.83 (0.04) | 0.03 (0.01, 0.06)c | 0.042 |
| Postprandial RQ (4-h mean) | 0.80 (0.04) | 0.83 (0.05) | 0.03 (.002, 0.06)c | 0.038 |
| RMR (kcal/day, n=9) | 1505 (262) | 1391 (180) | −147 (−253, −41)c | 0.010 |
Data are mean (SD) values (n=10 except for RMR where n=9). TIB-5.5h and TIB-8.5h: 5.5-h and 8.5-h time-in-bed conditions;
a
paired t-test comparisons;
b
beta coefficient (B) for the effect of sleep restriction (TIB-5.5h vs. TIB-8.5h) and its 95% confidence interval (CI) based on a mixed linear model controlling for crossover study design (treatment period as repeated measure) and baseline fat and fat-free body mass as time-varying covariates;
c
effect of sleep restriction in a mixed linear model controlling for treatment period and body composition at the end of each intervention.
REM: rapid eye movement; RQ: respiratory quotient; RMR: resting metabolic rate