In apparently healthy Korean adults, short sleep duration was associated with higher odds of MHO and MAO, most consistently MAO, but not robustly with MANW; the cross-sectional design precludes inference of causality.
The proportion of metabolically healthy normal weight (MHNW) rose steadily with longer sleep duration.
Sleeping ≤5 h/day was associated with higher odds of metabolically healthy obesity (MHO) relative to 7 h/day in the fully adjusted model.
Sleeping ≤5 h/day was associated with higher odds of metabolically abnormal obesity (MAO) relative to 7 h/day in the fully adjusted model.
When ≥9 h/day was used as the reference, no sleep duration associations were significant, including those with metabolically abnormal normal weight (MANW).
Under a stricter definition of metabolic health, the MAO association persisted while the MHO association lost statistical significance.
No significant effect modification by sex or age was observed for MHO or MAO.
The authors conclude short sleep is associated with obesity phenotypes, most consistently MAO, but causality cannot be inferred.
This study looked at nearly 7,800 Korean adults who had no known chronic diseases and asked whether how long they slept was related to their body weight and metabolic health. People were grouped into four types: normal weight with healthy metabolism, normal weight with unhealthy metabolism, obese with healthy metabolism, and obese with unhealthy metabolism. The researchers found that people who slept 5 hours or less a night were more likely to be in either obesity group (healthy or unhealthy metabolism) than people who slept 7 hours. The link was most consistent for obesity with unhealthy metabolism, which held up even under a stricter definition of metabolic health. The share of people with normal weight and healthy metabolism rose steadily with longer sleep, from about 62% among the shortest sleepers to 76% among those sleeping 9 or more hours. No clear link was found between short sleep and normal weight with unhealthy metabolism, and results did not differ by sex or age. Because this was a snapshot at one point in time and sleep was self-reported, the study cannot show that short sleep causes obesity or metabolic problems; it may be that the reverse is true or that other factors play a role. This research suggests short sleep is linked to obesity-related profiles, and longer follow-up studies are needed to see whether improving sleep could help metabolic health.
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Upload Your LabsKim E, Lee J, Lyu Y. (2026). Association Between Sleep Duration and Obesity Phenotypes in Apparently Healthy Korean Adults: A Cross-Sectional Study Using the Korea National Health and Nutrition Examination Survey 2013-2015.. Medicina (Kaunas, Lithuania). https://doi.org/10.3390/medicina62102014