The Impact of Early Bedtimes on Adolescent Caloric Intake Varies by Chronotype

Abstract

Purpose: Adolescent sleep restriction is common and can lead to overeating. Here, we test whether lengthening sleep via early bedtimes affects dietary intake differently for adolescents accustomed to a later sleep phase ("night owls") versus an earlier sleep phase ("morning larks").

Methods: Using a randomized cross-over design, 67 adolescents changed bedtimes to create five-night periods of sleep restriction (6.5 hours in bed) versus healthy sleep (10 hours in bed). Caloric intake was measured via validated interviews. Phase preference was based on participants' premanipulation sleep.

Results: Actigraphy verified that the manipulation altered sleep regardless of phase preference. Phase preference moderated the effect of the manipulation on cumulative caloric intake (p = .01-.03). Night owls showed little effect, but morning larks reduced their evening intake during healthy sleep.

Conclusions: An "early to bed" approach confers little dietary benefit for night owls but may have a protective effect for adolescents who gravitate toward earlier bedtimes.

Keywords: Adolescence; Caloric intake; Circadian preference; Dietary changes; Experimental sleep restriction; Sleep.