The claimEvidence B · meta-analysis
I'm a night owl, so staying up costs me nothing
The evidence
Being a night owl is heritable (Jones 2019, 351 gene locations), but being born late does not make staying up free. In overweight people, more social jet lag — the gap between workday and free-day sleep times — tracks with a higher BMI (Roenneberg 2012). Sleep enough, aligned to your rhythm.
The mechanism, in brief
The chapters so far are about what an all-nighter costs; this one goes back to the source: why do people stay up late? Part of it is an inborn body-clock rhythm, and part of it is habit — and the two have to be looked at separately, because the fixes are completely different.
Sources (2)
- Jones, S. E., Lane, J. M., Wood, A. R., van Hees, V. T., Tyrrell, J., Beaumont, R. N., et al. (2019). Genome-wide association analyses of chronotype in 697,828 individuals provides insights into circadian rhythms. Nature Communications, 10, 343. Identified 351 loci associated with morningness, confirming chronotype is substantially heritable; the most morning-leaning carriers slept ~25 min earlier.
- Roenneberg, T., Allebrandt, K. V., Merrow, M., & Vetter, C. (2012). Social jetlag and obesity. Current Biology, 22(10), 939-943. The mismatch between biological and social clocks (social jetlag) was positively associated with higher BMI among the overweight, linking circadian misalignment to weight.