Abstract 15465: Associations Between Adherence to the Physical Activity Goal and Body Fat Changes in a MHealth Weight Loss Trial

Abstract

Introduction: To date, few studies have examined the effectiveness of using wearable devices for promoting physical activity (PA) and improving body composition. Hypothesis: Adherence to the study-defined PA goal would be associated with greater body fat loss at 12 months than 6 months among adults with overweight or obesity during a weight loss intervention. Methods: SMARTER was a 12-mo, 2 arm weight loss trial with random assignment to (1) self-monitoring (SM, n=251) of diet, PA and weight, (2) self-monitoring plus ≤3 tailored feedback messages/day (SM+FB, n=251). The primary outcome was percentage of body fat % change assessed using Tanita scales and a body fat analyzer at 6 and 12 months relative to baseline. Adherence to the study-defined PA goal was assessed using weekly Fitbit moderate- and vigorous-intensity PA equivalents relative to ≥300 min/week PA goal and multiplied by 100%. Linear mixed modeling was used to estimate the effect of the percentage of adherence to the PA goal on the percentage of body fat % change at 6 and 12 months. Results: Participants (N=502) were mainly female (79.5%), White (82.5%), mean (± SD) age of 45.0 ± 14.4 years and BMI of 33.7 ± 4.0 kg/m2. Changes in the percentage of body fat % were similar at 6 and 12 months (time: F=3.48, P=.06) or by treatment assignment (treatment x time: F=1.33, P=.25). Overall, percentages of adherence to the PA goal were associated with greater percentages of body fat % loss (b [95% CI] -0.06 [-0.09, 0.03], F=18.61, P<.0001), which did not vary over time (PA adherence x time: F=2.88, P = .09). Finally, percentages of adherence to the PA goal moderated treatment effects (PA adherence x treatment: 0.05 [0.01,0.09], F = 4.69, P = .03), which did not vary over time (PA adherence x treatment x time: F = 0.29, P = .59). Conclusions: PA adherence was associated body fat loss, which did not vary at 6 and 12 months in adults with overweight or obesity. Future studies need to examine the effect of using wearable devices on body composition when targeting behavior changes.