Association of anthropometric measures with fat and fat-free mass in the elderly: The Rotterdam study

Objectives The decrease in fat-free mass (FFM) seen in many elderly people is usually associated with an increase in fat mass (FM), a state referred to as sarcopenic obesity. It is not clear which anthropometric measures are best used to identify sarcopenic obesity. We therefore evaluated which anthropometric measures are differentially associated with FM and FFM.
Main outcome and measures The anthropometric measures tested were body mass index (BMI), waist circumference (WC), and a body shape index (ABSI = WC/(BMI2/3∗Height1/2)). FM and FFM were estimated by dual-energy X-ray absorptiometry. An index-score was calculated for both FM (FMI) and FFM (FFMI) by dividing FM and FFM by height. Multivariable linear regression models were used to assess the associations of BMI, WC and ABSI with FMI and FFMI among 3612 participants (2092 women) from the prospective population-based Rotterdam Study.
Results In multivariate models adjusted for confounders, BMI and WC were positively associated with both FMI and FFMI in men and women. ABSI was positively associated with FMI (β 1.01, 95% confidence interval (95%CI) 0.85, 1.17) and negatively associated with FFMI (β -0.28, 95%CI -0.38, -0.17) in men. In women, ABSI was not associated with FMI and was positively associated with FFMI (β 0.18, 95%CI 0.10, 0.26).
Conclusions While BMI and WC were both positively associated with FM and FFM, ABSI showed a differential association with FM and FFM in men, but not in women. Since sarcopenic obesity is associated with decreased FFM and increased FM, ABSI could be a useful tool for identifying men at higher risk of sarcopenic obesity.