Longitudinal changes in physical activity and dietary fat intake during an intensive lifestyle intervention: the PROPEL trial.

Lifestyle modifications including physical activity and dietary changes are considered the cornerstone approach for behavioral obesity management. However, there is a lack of knowledge about long-term trajectory patterns during interventions. This study aims to (1) assess physical activity and dietary fat intake trajectory during a 24-month intensive lifestyle intervention; and (2) identify baseline characteristics and sociodemographic predictors associated with different behavioral trajectory patterns. The PROPEL trial recruited and randomly assigned primary care clinics to a 2-year intensive lifestyle intervention or a usual care group. A total of 439 individuals (88.4% female, 73.8% Black) enrolled in the intervention group. Participants were included in the analysis if they provided valid data for physical activity and dietary fat intake at a minimum of 2 of the 4 assessment time points. Physical activity was measured via the short-form International Physical Activity Questionnaire, and the percentage of energy from fat was measured using a validated fat screener. A group-based trajectory model was used to identify the physical activity and dietary fat intake trajectory groups. Multilevel multinomial logistic regression models were used with the dependent variable of trajectory group membership, adjusting for baseline covariates. All statistical analyses were performed using R statistical software (version 4.4.2, macOS), and P < .05 was considered statistically significant. Trajectory analysis identified 5 groups of physical activity and dietary fat intake over 24 months. Group 1 (21%) maintained moderate physical activity with a gradual decrease after 6 months, accompanied by an initial fat reduction that plateaued at 31%. Group 2 (16%) had low activity levels while showing a U-shaped fat intake during the intervention. Group 3 (33%) reached a peak of high activity at 6 months before declining, maintaining the lowest percentage of fat intake. Group 4 (20%) increased activity through 12 months with a reverse U-shaped change and with fat reduction, while group 5 (10%) also had low activity and persistently high fat intake. Multinomial regression indicated that participants with diabetes at baseline were more likely to be classified as group 5 with a lower activity level and high dietary fat intake. Identifying the trajectory of behavior can facilitate the development of more tailored interventions, particularly for long-term behavior change.