Increased energy intake following sleep restriction in men and women: A one-size-fits-all conclusion?
Level 2 - randomized trial
Pooled analysis of two randomized crossover trials
PubMed 28401667 · doi:10.1002/oby.21831
What was done
Data were combined from two randomized crossover trials involving 43 healthy, non-smoking, normal-weight adults (mean age 31 ± 7 years, BMI 23 ± 2 kg/m²) who were non-shift workers sleeping 7 to 9 hours nightly at baseline. Participants underwent both sleep restriction (3.5 to 4 hours in bed per night) and habitual sleep (7 to 9 hours in bed per night) conditions. Objective 24-hour ad libitum energy intake was measured. The study analyzed individual variation in energy intake changes (ΔEI) and assessed age, sex, ethnicity, BMI, study site, and protocol order as potential contributors.
What was found
Interindividual variation in energy intake changes (ΔEI) between sleep restriction and habitual sleep ranged from -813 to 1437 kcal/day. Only protocol phase order was significantly associated with ΔEI (β = -568 kcal/d, 95% CI -921 to -215 kcal/d; P = 0.002); participants randomized to habitual sleep first had greater increases in energy intake during sleep restriction (P = 0.01). Age, sex, ethnicity, BMI, and study site showed no significant association with ΔEI.
Why it matters
This study shows that increased caloric intake following sleep restriction is not a uniform response and identifies a substantial phase-order effect that must be accounted for in crossover sleep trials.
Limits
The total sample is small (n = 43) and pooled across two distinct trial sites. Participants were restricted to young, healthy, normal-weight adults without sleep disturbances, limiting generalizability to populations with obesity or chronic sleep deficits. The strong protocol-order effect introduces methodological confounding that complicates direct causal interpretation of sleep restriction alone. Long-term dietary patterns outside laboratory-controlled ad libitum access were not evaluated.