Fat Modulates the Relationship between Sarcopenia and Physical Function in Nonobese Older Adults

It is intuitive to think that sarcopenia should be associated with declines in physical function though recent evidence questions this assertion. This study investigated the relationship between absolute and relative sarcopenia, with physical performance in 202 nonobese (mean BMI = 26.6 kg/ht 2 ) community-dwelling older (mean age = 73.8 ± 5.9 years) adults. While absolute sarcopenia (appendicular skeletal mass (ASM)/ht 2 ) was either not associated, or weakly associated with physical performance, relative sarcopenia (ASM/kg) demonstrated moderate (r = 0.31 to r = 0.51, P < 0.01) relationships with performance outcomes in both males and females. Knee extension strength (r = 0.27) and leg extension power (r = 0.41) were both related to absolute sarcopenia ( P < 0.001) in females and not in males. Strength and power were associated with relative sarcopenia in both sexes (from r = 0.47 to r = 0.67,  P < 0.001). The ratio of lean mass to total body mass, that is, relative sarcopenia, is an important consideration relative to physical function in older adults even in the absence of obesity. Stratifying these individuals into equal tertiles of total body fat revealed a trend of diminished regression coefficients across each incrementally higher fat grouping for performance measures, providing further evidence that total body fat modulates the relationship between sarcopenia and physical function.