Gavin, Kara2017-11-272017-11-272017-08https://hdl.handle.net/11299/191356University of Minnesota Ph.D. dissertation. August 2017. Major: Epidemiology. Advisor: Jennifer Linde. 1 computer file (PDF); x, 116 pages.This dissertation consists of three investigations covering topics on physical activity achievement and continuation and its relationship with body weight in two intervention samples. The data for the first two papers come from the Tracking Study weight loss intervention trial, while data for the third paper come from the Stand & Move at Work group-randomized worksite LPA intervention trial. Manuscript 1 examined the relationship between the occurrence of life events, MVPA achievement and weight loss maintenance success following a lifestyle weight loss intervention using a 4-way mediation and moderation decomposition analysis. Findings suggested that the effects of life events and MVPA on weight loss maintenance should be considered as separate effects when considering weight loss maintenance and designing interventions to prevent weight re-gain. Manuscript 2 utilized behavior-tracking logs during a weight loss intervention to identify individuals who may show signs of behavioral disengagement and increased weight. General Estimating Equation (GEE) modeling was used to examine the association between physical activity self-monitoring characteristics and reported MVPA participation and weight measured at 12-month and 24-month follow-up. Results showed various self-monitoring characteristics were associated with MVPA participation and weight at 12- and 24-month time points, suggesting that behavior-tracking characteristics should be used to monitor intervention engagement. Manuscript 3 explored differences in LPA participation by BMI category. Hierarchical models examined the association of BMI category with baseline work time LPA participation, total daily LPA participation, and work time LPA participation over time from baseline to 3 months. At baseline there were no statistical differences in work time LPA participation across BMI categories. At three months, participants with BMI in normal and overweight categories participated in work time LPA longer than participants with BMI in the obese category. The findings of this dissertation inform future intervention design and measurement implications for behavioral science and epidemiology.enBehavioral MaintenanceBehavior ChangePhysical AcvtityWeight lossThesis or Dissertation