A randomized controlled trial to evaluate self-determination theory for exercise adherence and weight control: rationale and intervention description

Abstract

Background: Research on the motivational model proposed by Self-Determination Theory (SDT) provides theoretically sound insights into reasons why people adopt and maintain exercise and other health behaviors, and allows for a meaningful analysis of the motivational processes involved in behavioral self-regulation. Although obesity is notoriously difficult to reverse and its recidivism is high, adopting and maintaining a physically active lifestyle is arguably the most effective strategy to counteract it in the long-term. The purposes of this study are twofold: i) to describe a 3-year randomized controlled trial (RCT) aimed at testing a novel obesity treatment program based on SDT, and ii) to present the rationale behind SDT's utility in facilitating and explaining health behavior change, especially physical activity/exercise, during obesity treatment.

Methods: Study design, recruitment, inclusion criteria, measurements, and a detailed description of the intervention (general format, goals for the participants, intervention curriculum, and main SDT strategies) are presented. The intervention consists of a 1-year group behavioral program for overweight and moderately obese women, aged 25 to 50 (and pre-menopausal), recruited from the community at large through media advertisement. Participants in the intervention group meet weekly or bi-weekly with a multidisciplinary intervention team (30 2 h sessions in total), and go through a program covering most topics considered critical for successful weight control. These topics and especially their delivery were adapted to comply with SDT and Motivational Interviewing guidelines. Comparison group receive a general health education curriculum. After the program, all subjects are follow-up for a period of 2 years.

Discussion: Results from this RCT will contribute to a better understanding of how motivational characteristics, particularly those related to physical activity/exercise behavioral self-regulation, influence treatment success, while exploring the utility of Self-Determination Theory for promoting health behavior change in the context of obesity.

Trial registration: Clinical Trials Gov. Identifier NCT00513084.

Figure 1

Model Describing Internalization and Human Motivation. Model shows different types of motivation and regulation continuum reflecting varying degrees of internalization and self-determination. This continuum reflects a simplex-ordered structure, evident when the correlation between scales measuring adjacent types of motivation such as external regulation and introjected regulation is higher than the correlation between dimensions that lie further apart such as external regulation and identified regulation. Adapted from [68].

Figure 2

The Self-Determination Theory Model for maintained behavior change. Model presents key constructs of health behavior change (scales used also) and the expected relationships among them. Autonomy (both as individual orientation and experimentally promoted) is central to maintained behavior change through is effects on competence and self-regulation. See Methods for abbreviations. Adapted from [29].

Figure 3

Relations Between Psychological Needs and Motivational Styles From Self-Determination Theory and the Core Principles from Motivational Interviewing. Parallels between MI main strategies and factors that are considered in SDT to facilitate integration are striking, providing a theoretical framework for understanding how change occurs. The construct of need satisfaction, as conceptualized within SDT, provides a useful way to understand the positive effects of motivational interviewing. Adapted from [38].