The relationship between pedometer-determined ambulatory activity and body composition variables

OBJECTIVE: To examine the relationship between pedometer-determined ambulatory activity (steps/day) and body composition variables body mass index (BMI) and percentage body fat). DESIGN: Secondary analysis of a cross-sectional objective activity monitoring study for up to 21 consecutive days. SUBJECTS: A total of 109 apparently healthy adults (eight African American males, 23 African-American females, 33 Caucasian males, 45 Caucasian females), age 44.9 +/- 15.8 y, BMI = 26.9 +/- 5.1 kg /m(2). MEASUREMENTS: Pedometer-assessed ambulatory activity (steps/day), height and weight, and percentage body fat by bioelectrical impedance. RESULTS: Analyzed as both a continuous and a categorical variable (determined using 25th and 75th percentiles for distribution for steps/day), ambulatory activity was consistently related to body composition variables. Steps/day was inversely correlated with BMI and percentage body fat (r = -0.30, and r = -0.27, respectively, both P < 0.01). The consistency of the relationship was also evident when examined using accepted BMI cut-off points for normal-weight, overweight, and obese categories. CONCLUSIONS: Individuals in this small sample with values greater than approximately 9000 steps/day are more frequently classified as normal weight for height. Individuals with values less than approximately 5000 steps/day are more frequently classified as obese. These findings require further corroborative investigation but provide preliminary cutoff points for identifying individuals at risk who may benefit from appropriate physical activity intervention.