In 122 postmenopausal women (mean age 58.1 years, mean BMI 33.2 kg/m²), later sleep onset was significantly associated with greater visceral adipose tissue measured by DXA (p=0.0007). A random forest model ranked sleep onset time, sleep duration, and time of last caloric intake as the top three predictors of visceral fat — outranking other metabolic markers including insulin resistance, blood pressure, and triglycerides, none of which reached significance independently.
Visceral adipose tissue is among the most metabolically dangerous fat depots, driving cardiovascular risk, insulin resistance, and systemic inflammation. This finding adds to a growing body of circadian-metabolic research linking late chronotype and delayed eating windows to worse cardiometabolic profiles — reinforcing advice that both when you sleep and when you eat matter, not just how long. For postmenopausal women specifically, who lose estrogen's protective regulation of eating and activity rhythms, sleep timing may represent an underappreciated lever for metabolic health management.
Important caveats apply: this is a cross-sectional design, so causality cannot be established — heavier visceral fat may itself disrupt sleep rather than the reverse. The cohort is also exclusively postmenopausal women with overweight or obesity, limiting generalizability. As a preprint posted on medRxiv and not yet peer-reviewed, findings could change after formal scrutiny. Still, the study's actionable implication — that advancing bedtime could reduce visceral fat — is clinically plausible and worth discussing with physicians.