Effect of Sleep Extension on Objectively Assessed Energy Intake Among Adults With Overweight in Real-life Settings

This randomized clinical trial examines the energy intake, energy expenditure, and body weight in adults who slept less than 6.5 hours per night.

hygiene counseling via a structured, face-to-face interview of approximately 1-hour duration. The overall goal was to accommodate extended bedtimes in participants' lifestyles in the best possible way. First, actigraphy data from baseline period was briefly reviewed with the participant. Next, the key components of sleep hygiene were discussed. Specifically, the habitual sleep-wake schedules on workdays and free days, naps (if any), environmental factors (bedroom temperature, noise, ambient light), bedtime routine, television/electronic use, and physiological factors (e.g., exercise, caffeine) were reviewed. As necessary, factors related to sleep partner, children, other household members and pets were considered. Individual recommendations on sleep hygiene were provided to better implement extended bedtimes into the daily routine. At the end of the interview, participants were provided with individualized bedtime and wake-up time schedules to follow at home for two weeks, aiming to extend bedtime duration to 8.5 h. The schedules were designed by mutual agreement considering personal schedules and priorities. On day 22, participants returned for a brief follow-up visit of approximately 15-min. Actigraphy data from the first intervention week was reviewed and further sleep counseling was provided, as needed.

Doubly Labeled Water Method
We measured total energy expenditure using the doubly labeled water method. 1-3 This method measures the sum of energy expenditure for resting metabolic rate, thermic effect of meals and physical activity. On day 1, participants reported to the research unit in the morning after an overnight fast. Participants completely voided to collect pre-dose urine specimen and two 5 mL aliquots were transferred to o-ring sealed, screw capped Corning cryotubes. Subjects drank a sterile loading dose of 1.8 g 10 AP 18 O and 0.12 g 99.9 AP 2 H enriched water per kg of estimated total body water. The dose bottle was washed with 50 g of tap water which was consumed by the participants. Subjects voided at 1 hour after the dose and that specimen was discarded.
Participants voided again at 3 hours and 4 hours after the dose and aliquots were collected.
Participants fasted throughout the 4-h specimen collection period. They were provided 250 mL water between 1-h and 3-h post dose, and the water consumed was recorded and subtracted from the total body water. Participants returned to the research unit on the morning of day 14 after an overnight fast and two voids were collected 1 hour apart, and aliquots stored. Urine specimens were stored at -20ºC and shipped to the University of Wisconsin-Madison for analysis. The rate of CO 2 production was calculated using Schoeller equation A6 as modified by Racette et al (1994). 2,4 TEE was calculated from rCO 2 as described by Black et al. 5 , assuming participants consumed a typical diet with a food quotient of 0.86 individually accounting for the change in mass of protein and fat during each 2-week period. 6 For each 2-week period, the change in body energy stores was computed from the regression (slope, grams/day) of daily home weights and change in body composition i.e., fat mass (FM) and fat free mass (FFM) as measured by dual-energy x-ray absorptiometry.

Resting metabolic rate and thermic effect of meal and activity energy expenditure.
Resting metabolic rate (RMR) was measured by indirect calorimetry using the DeltaTrac (SensorMedix) and Vmax (SensorMedix) metabolic carts. The same unit was used in any given participant during baseline and treatment periods. Participants reported to the research unit in the morning after an overnight fast. After calibration against a standard gas mixture and 30 minutes of resting period in a semi-recumbent position in bed, a clear plastic canopy and flexible plastic seal was placed over participant's head and respiratory gas exchange was measured for 40 minutes.
The first 10 minutes of measurements were discarded to collect data under steady state. The subjects then consumed a standardized breakfast (liquid meal) within 5 minutes. Thermic effect of the meal was measured using the same metabolic cart over the next 4 hours using a protocol of 50 min under the canopy and followed by 10 min with the canopy removed in a repeated cycle for participants' comfort. Thermic effect of meal was calculated as previously described. 7 Activity energy expenditure was calculated by subtracting the resting metabolic rate and thermic effect of meal from the total energy expenditure measured by doubly the labeled water method. 7 Data were reported as mean (SD) unless otherwise specified. At the end of 4-week study, participants were asked questions using visual analog scales about their experience during the preceding 2-week i.e., intervention period. The visual analog scales (score 0 to 100) included a straight line extending from left end of the scale (i.e., score 0, "Strongly disagree") to the right end of the scale (i.e., score 100, "Strongly agree"). Participants completed the visual analog scales in REDCap by marking any point on the continuous line that corresponds to their subjective agreement to the questions. P values for the differences between groups (extension group -control group) are from two sample t-tests assuming unequal variances (Satterthwaite's approximation).