Magnetic Resonance Imaging-defined visceral adiposity beyond Body Mass Index is associated with insulin resistance and early glycemic dysregulation in adults without diabetes.

OBJECTIVE

- To determine whether magnetic resonance imaging-quantified visceral adiposity beyond that expected from body mass index (BMI) is associated with adverse metabolic phenotypes in adults without diabetes and more strongly than abdominal subcutaneous fat.

METHODS

- This community-based cross-sectional study included 474 adults aged 40-65 years without diabetes. Visceral fat area (VFA) and subcutaneous fat area (SFA) were measured by magnetic resonance imaging. Sex-specific BMI-adjusted residual phenotypes were constructed, and associations with oral glucose tolerance test-derived metabolic outcomes were examined using multivariable regression.

RESULTS

- Each 1-SD increase in BMI-adjusted VFA was associated with a lower Matsuda index (β=-0.41), higher log HOMA-IR (β=0.10), higher 2-hour glucose (β=0.22 mmol/l), greater glucose area under the curve (β=16.34 mmol/l × min), and lower oral disposition index (β=-9.10). BMI-adjusted SFA was not significantly associated with these outcomes. BMI-adjusted VFA was also associated with WHO-defined prediabetes (OR=1.32) and isolated impaired glucose tolerance (OR=1.33), with stronger associations than BMI-adjusted SFA, but not with ADA-defined prediabetes (OR=0.89, 95% CI 0.70-1.12).

CONCLUSIONS

- Visceral adiposity beyond BMI identified an adverse fat-distribution phenotype characterized by reduced insulin sensitivity, impaired post-load glucose handling, and inadequate β-cell compensation. Regional fat distribution may refine obesity phenotyping beyond BMI.