Latent Profile Analysis of Physical Activity Motivation during Behavioral Weight Loss Treatment.

Participants in behavioral weight loss (BWL) treatment often struggle to meet and maintain physical activity (PA) prescriptions; improving participants' motivation for the behavior is a potential intervention strategy. Self-Determination Theory (SDT) outlines a continuum of qualitatively different dimensions of motivation, suggesting that more self-determined forms of motivation should predict more PA, whereas less self-determined forms of motivation should be unrelated or negatively related to PA. Although SDT has ample empirical support, most existing research in this area has used statistical analyses that oversimplify the complex, interdependent relationships between dimensions of motivation and behavior. This study's purpose was to explore commonly occurring motivational "profiles" for PA based on the SDT dimensions of motivation (amotivation, external, introjected, integrated/identified, and intrinsic motivation) and how these profiles relate to PA behavior among participants with overweight/obesity (N=281, 79.4% female) at baseline and six months into BWL treatment. Latent profile analysis determined that three motivational profiles fit the data best at both timepoints and the profile characterized by high self-determined (i.e., integrated/identified and intrinsic) motivation and moderate introjected motivation was by far the most common. There were no differences in physical activity behavior across motivational profiles, which contrasts previous literature. Findings suggest that participants who take the initiative to sign up for intensive BWL programs may have sufficiently high PA motivation, which may be a poor predictor of their actual behavior. Future research should examine these relationships later in treatment, when motivation may have more variability, as well as among participants who initiate lower-commitment weight loss programs (e.g., self-help).