Nonlinear relationship between waist to hip ratio, weight and strength in elders: is gender the key?

Visceral fat has a high metabolic activity with deleterious effects on health contributing to the risk for the frailty syndrome. We studied the association between waist to hip ratio (an indirect measure of visceral fat stores) on upper and lower extremities strength. 1741 individuals aged ≥65 participated in this study. The data was obtained from the Toledo Study for Healthy Aging. For each gender, we studied the relationship between the waist-to-hip ratio (WHR), body mass index (BMI) and regional muscle strength (grip, shoulder, knee and hip) using multivariate linear regression and kernel regression statistical models. WHR was higher in men than in women (0.98 ± 0.07 vs. 0.91 ± 0.08, respectively, P < 0.05). In women with high WHR, we observed a decrease in strength especially in those with a normal BMI. As the WHR lowered, the strength increased regardless of the BMI. In men, lower strength was generally related to the lowest and highest WHR's. Maximum strength in men corresponded at a WHR around 1 and the highest BMI. Muscle strength depends on the joined distribution of WHR and BMI according to gender. In consequence, sex, WHR and BMI should be analyzed conjointly to study the relationship among fat distribution, weight and muscle strength.