Associations of appendicular lean mass and abdominal adiposity with insulin resistance in older adults: A cross-sectional study

Loss of lean muscle mass and accumulation of adipose tissue are changes associated with aging. Previous studies have documented various components of body composition as predictors for insulin resistance. The objective of this study was to investigate whether components of body composition-appendicular lean mass (ALM) and/or abdominal fat mass (AFM)-correlate with insulin resistance in older men and women. This was a cross-sectional study of 92 older men and women. Weight was classified according to body mass index (BMI)-normal (BMI <25), overweight (BMI 25-30), and obese (BMI >30). All body composition data was determined by dual energy x-ray absorptiometry (DEXA), and insulin resistance was assessed by the homeostatic model assessment of insulin resistance (HOMA-IR). Multivariable regression models with two-way interaction terms were employed to assess whether the associations between components of body composition and log HOMA varied by BMI categories. Adjusted regression showed that log HOMA was significantly associated with AFM (estimate +/- standard error: 0.055 +/- 0.026) and ALM (0.057 +/- 0.029) for the overweight participants (p-values <0.05). Additionally, the adjusted associations between log HOMA and ALM were significantly greater for participants who were either obese or overweight compared to those with a normal BMI (p<0.002). Less consistent relationships were observed between insulin resistance and abdominal fat mass across BMI categories, whereas more consistent associations were observed between insulin resistance and appendicular lean mass in individuals with greater BMI. Further research is needed to clarify if lipid deposition within muscle tissue promotes muscle dysfunction and thereby increases risk for insulin resistance.