To assess the association between functional limitations and body composition indices, including percentage of body fat, muscle mass, and body mass index (BMI). A cross-sectional, population-representative sample. All noninstitutionalized people living in the United States (National Health and Nutrition Examination Survey). Data were collected between 1988 and 1994. One thousand five hundred twenty-six women and 1,391 men aged 70 and older. Independent variables included BMI, muscle mass, and percentage of body fat; the latter two were assessed using predictive equations. The dependent variable, functional limitations, was defined as difficulty in performing at least three of five functional living tasks, such as carrying a 10-pound bag of groceries. Women in the highest quintile for percentage of body fat and women with a BMI of 30 or greater were two times more likely to report functional limitations than women in the comparison groups. Similar, but weaker, relationships were found among men; men in the highest quintile for body fat and men with a BMI of 35 or greater were 1.5 times more likely to report limitations. Low muscle mass (sarcopenia) and sarcopenia in combination with high percentage of body fat (sarcopenic obesity) were not associated with a greater likelihood of reporting functional limitations. Prevention of excessive accumulation of body fat and maintenance of a BMI in the normal range may reduce the likelihood of functional limitations in old age.
