Sleep extension reduces energy intake in free-living overweight adults: a randomized controlled study

Introduction: Substantial evidence suggests that short sleep duration increases obesity risk. However, evidence is lacking as to whether an intervention aimed to increase sleep duration in individuals who habitually curtail their sleep has beneficial effects on energy balance. Here, we present data from an ongoing randomized controlled trial investigating the effects of sleep extension on energy metabolism in habitual short sleepers, while they live in their normal home environment without any prescribed diet or physical activity. Methods: Overweight, otherwise healthy adults (21-40 years) who habitually sleep < 6.5 hours per night (confirmed by actigraphy) were recruited from the community. After 2-weeks of habitual sleep [baseline], participants were randomized to either 2-weeks of sleep extension (Extension group) with 8-hour bedtimes, or 2-weeks of continued habitual sleep (Control group). Participants who were randomized to sleep extension received individualized counseling on sleep hygiene on the first day of the intervention. Total energy expenditure (TEE) was measured using the gold standard doubly-labeled water method. Home weights were measured daily by participants in the morning. Change in body energy stores was computed using the regression of home weights and body composition (fat mass, fat free mass) as measured by serial DEXA scans. Energy intake (Ei) was calculated from the energy balance equation as Ei=TEE+change in body energy stores. Sleep was continuously assessed by wrist actigraphy. Results: To date, the data is available from a total of 60 participants (Extension group n=30; Control group n=30). Baseline characteristics including age, gender, ethnicity, BMI, work status, exercise habits and habitual sleep duration were similar between groups (Table-1). Sleep duration was increased by ∼1.2 hours (p< 0.0001) in the extension group as compared to control group. TEE tended to decrease (treatment effect= -79 kcal/day, p=0.08) with sleep extension as compared to habitual sleep. Sleep extension, as compared to habitual sleep resulted in significantly lower Ei (treatment effect= -207 kcal/day, p=0.021). The results were similar after controlling for gender and menstrual cycle. Conclusions: These findings provide the first evidence that sleep extension reduces objectively measured energy intake in real-life settings in overweight individuals who habitually curtail their sleep. Using Hall's dynamic model of weight re-equilibrium, a 128 kcal/day deficit in energy balance that we observed after 2-week sleep extension intervention, would predict ∼6 kg decrease in weight after 3 years. These predictions suggest that, if healthy sleep habits are maintained over extended time periods, this would translate into clinically significant weight loss.