The relationship between internal experiences and physical activity and the moderating role of acceptance-based psychological processes in people with overweight and obese BMIs
Authors:   , Remmert Jocelyn E. , Butryn Meghan L. 
Published: July 2021

Rationale: There are low rates of physical activity in adults with overweight and obese BMIs. Internal experiences may be an important and under-addressed determinant of physical activity behavior, however they have not been measured with objectively measured physical activity in people with overweight or obese BMIs; therefore this study's first aim is to address this gap. The study's second aim is to examine a new approach to physical activity promotion that is based in acceptance, which has preliminary evidence in interventions but the theoretical model has not been directly tested. Methods: Adults (n=320) rated their internal experiences during a treadmill walking task at baseline of a behavioral weight loss trial. Participants also completed measurements of physical activity (accelerometer) and acceptance-based psychological processes (self-report) at baseline. Accelerometer measurement of physical activity was repeated six months after initial behavioral weight loss. Compound poisson linear models were utilized to test the relationships between internal experiences, acceptance-based psychological processes, and physical activity. Results: Higher ratings of energetic and strength were both separately positively associated with concurrent physical activity. Discomfort tolerance moderated the relationship between ratings of weak/strong and physical activity, and perceived exertion and physical activity. Other significant moderation models yielded results contrary to hypotheses, such that acceptance-based psychological processes had a larger effect at positive internal experiences. No model significantly predicted physical activity at six months. Conclusions: Results from the first aim suggest that there is divergence in the relationships between different internal experiences and physical activity, and it may be clinically helpful to include more specific measurement of internal experiences in future studies. Results from the second aim suggest that discomfort tolerance may be a key skill in physical activity promotion. However, overall acceptance-based psychological processes had a larger effect on positive internal experiences, suggesting that a positive affective experience may be necessary to create an environment conducive to skill utilization. Additionally, no models significantly predicted physical activity at six-months, suggesting that other factors such as the changes during weight loss may be more salient to physical activity engagement at six-months. Limitations in methodology and measurement of the internal experience and acceptance-based psychological processes are discussed. This study is the first to examine internal experiences, acceptance-based psychological processes, and objectively measured physical activity in adults with overweight or obese BMIs. Future studies should address the limitations of this study to further investigate the theoretical model of acceptance-based interventions for physical activity.