The Influence of Body Mass Index on Self-report and Performance-based Measures of Physical Function in Adult Women

Little is known about limitations in physical function across BMI categories in middle aged women using both self-report and performance-based measures. Furthermore, the impact of BMI on the measurement of function has not been explored. The purpose of this study was to assess physical function in adult women across BMI categories using self-report and performance-based measures and determine the influence of BMI on the relationship between the measures.

Fifty sedentary females (10 in each BMI category: normal weight, overweight, obese class I, II, and III) aged 51.2 ± 5.4 years participated. Assessments included demographics, past medical history, physical activity level, BMI, and self-report (Late Life Function and Disability Instrument) and performance-based measures of physical function (6-Minute Walk Test, timed chair rise, gait speed). Physical function was compared between BMI categories using analysis of variance. The influence of BMI on the relationship of self-report and performance-based measures was analyzed using linear regression.

Compared to those that were normal weight or overweight, individuals with obesity scored lower on the self-report measure of physical function (LLFDI) for capability in participating in life tasks and ability to perform discrete functional activities. On the performance-based measures, the individuals with obesity had slower gait speed compared to the normal and overweight weight groups. For the 6-Minute Walk Test and timed chair stands, individuals with obesity had poorer performance compared to those who were normal weight. Linear regression analyses revealed that BMI attenuated the relationship between the self-report and performance-based measures by approximately 50%.

While those with severe obesity were most impaired, adult women with less severe obesity also demonstrated significant decrements in physical function.