Associations of Daily Physical Activity and Sedentary Behavior with BMI in Older Women

Abstract

To sustain a healthy weight, 75-150 mins/wk of moderate-vigorous intensity physical activity (MVPA) are recommended. As PA declines with age, accurate PA measurement in older adults is crucial but challenging. Recent reports suggests that too much sedentary time also affects weight and distributing PA (including low intensity; LPA) throughout the day is important in addition to total PA time. PURPOSE: To determine the importance of considering PA variations during the day for BMI management in older women. METHODS: Eleven older women (age 77±9 yrs; BMI 26±5 kg/m2) wore activity monitors, each containing a tri-axial accelerometer (±16g, 100 Hz), on the waist and ankle for 4 days in the free-living environment. IRB approved the protocol and written informed consent was obtained. Daily step counts, active time (classified as MVPA for cadence>94 steps/min) and sedentary break number (number of activity segments ≥30 s) were estimated from acceleration data using a previously validated algorithm. The parameters’ total daily values and coefficient of variations (CoVs) of hourly values (to quantify variation during the day) correlations with BMI were assessed with linear regression. RESULTS: BMI was inversely correlated with active and MVPA time, step counts, and sedentary break number (Fig 1) consistent with associations of greater activity with healthier weight. BMI was positively correlated with the CoVs of active time/hour, step number/hour, and sedentary break number/hour (Fig 1), with higher r2 values compared to daily totals. CONCLUSION: The data highlight the importance of breaking up sedentary time with both LPA and MVPA, and distributing PA throughout the day to sustain a healthy BMI. Funded by DOD DM090896 and NIH RO1 AR027065.