Relatively lower BMI-adjusted calf circumference is associated with metabolically unhealthy phenotype in non-obese adults: a cross-sectional study.

Background: Metabolically unhealthy non-obese (MUNO) individuals are at higher risk of cardiovascular diseases, while not receiving sufficient attention. This study was conducted to explore the association between BMI-adjusted CC and MUNO in non-obese US adults using the NHANES database.

Methods: A total of 9,628 non-obese US adults (48.01% female and 51.99% male) were included in this cross-sectional study. The metabolically unhealthy phenotype was defined as ≥ 2 components of metabolic abnormalities. BMI-adjusted CC and BMI-adjusted skeletal muscle mass (SMM) were divided into quartiles. Weighted multiple logistic regression model was used to evaluate the study aims. The relation between BMI-adjusted CC and BMI-adjusted SMM was tested by Spearman correlation.

Results: In the multivariate analysis, compared with the lowest quartile of BMI-adjusted CC and BMI-adjusted SMM, OR (95%CI) of the highest quartile was 0.30 (0.25, 0.35) (P < 0.001, P for trend < 0.001) and 0.39 (0.29, 0.53) (P < 0.001, P for trend < 0.001), respectively. BMI-adjusted CC was positively correlated with BMI-adjusted SMM for all participants (r = 0.48). A weak non-linear association was observed in BMI-adjusted CC and MUNO (P = 0.047). Similar results were observed in sex- and BMI-specific subgroup and sensitivity analysis.

Conclusion: BMI-adjusted CC was inversely associated with MUNO, suggesting more attention should be paid to monitoring BMI-adjusted CC for the public to ease the disease burden, especially for people without obesity.