What are the purposes of the present study?

To date, the prevalence of obesity and being overweight has increased rapidly. Recent research for instance found that 51.6% of Portugese adults struggle from being overweight of having obesity. Obese is a major health problem, that is associated with various chronic disease risk factors, dysphoric states, and psychological problems. Weight loss is recommended in various intervention programs. Unfortunately, however, research has found that only a small share of the weight loss accomplished in treatment programs is maintained over the long term. That is, only about 20% of the individuals that seek weight loss programs are able to successfully integrate certain activity behaviors into their daily life and achieve long-lasting weight loss. Hence, there is a strong need for research that identifies reliable predictors of successful weight-loss maintenance and to test interventions that specifically promote weight stability after weight loss.

The present study addressed the following two purposes:

1. To present the rationale behind SDT's utility in facilitating and explaining health behavior change, in particular concerning physical activity and exercise during obesity treatment.
2. To describe a 3-year randomized controlled trial (RCT) aimed at testing a novel obesity treatment program based on the self-determination theory (SDT).

What is the rationale behind SDT and motivation for changes in health behavior?

Many studies have indicated the crucial role of motivation in adherence to certain healthy behaviors. Motivation concerns the psychological forces or energies that impel a person toward a specific goal. For a long time, motivation was considered unidimensional, hence only allowing variances in amount or quantity. To date, the quality of motivation is stressed more. In the self-determination theory (SDT), developed by Deci and Ryan, a distinction is made between amotivation (lacking any intention to engage in a certain behavior), extrinsic motivation (where the behavior is engaged in order to achieve an outcome that is separable from the behavior itself), and intrinsic motivation (where the behavior is engaged in for the enjoyment and satisfaction inherent in taking part). Within extrinsic motivation, a further distinction can be made between autonomous or self-determined types of behavioral regulation versus controlled or non-self-determined types of behavioral regulation. Motivation then, can be both autonomous to the extent that someone's perceived locus of causality is internal, as well as viewed external, thus having an external perceived locus of causality (people act in a certain way because they feel pressured or compelled to do so).

According to the SDT, there are four types of extrinsic motivation that are placed on a continuum:

1. External regulation: doing something to obtain a reward or to avoid punishment by others.
2. Introjected regulation: an internal feeling of obligation, doing something to avoid feelings of guilt.
3. Identified regulation: doing something based on the value of its consequences (because the outcomes are personally important).
4. Integrated regulation: doing something because it is coherent with the person's other values, personality schemes and sense of self.

Internalization then can be described as movement along this continuum.

According to the SDT, formerly controlled motivation can be internalized and transformed into autonomous motivation, if supportive conditions are met. In particular the three basic psychological needs should be satisfied: autonomy, relatedness, and competence.

Transferring this to the weight control interventions, a successful weight control would occur if someone chooses eating and exercising because he or she personally values weight loss maintenance and its associated health benefits. Current research therefore focuses on the mechanisms that promote such self-determined motivation for healthy behavior. Factors that appear to play a role are: enjoyment, perceptions of competence, and intrinsic reasons for participants. This is summarized in the SDT model for maintained behavior change. In this model, autonomous self-regulation plays a central role. Further, autonomous self-regulation and perceived competence are in turn expected to increase maintained change of the healthy behaviors.

What are the characteristics of the 3-year RCT aimed at testing a novel obesity treatment program based on SDT?

In this section, a randomized controlled trial (SDT) is described, that analyzes 3-year change in health behavior. The RCT consisted of a 1-year behavior change intervention program and a 2-year follow up period without an intervention. The 259 female participants (25-50 years old) were split into two random groups: one intervention group and one control group. The participants in the intervention group attended approximately 30 group sessions during one year. These sessions took about 120 minutes and included educational content where information was provided by physical activity, nutrition, and behavior change specialists. The sessions also consisted of an interactive discussion as well as small group activities. The initial emphasis of the program was on inducing some weight loss. Subsequently, the focus changed to cognitive and behavioral aspects, increasing knowledge, and improving body image. Further, the intervention focused on promoting self-determination. This was done via the following mechanisms:

• Offering a clear rationale to adopt a certain behavior.
• Acknowledging internal conflicts: usual patterns versus a desire to adopt new behavior.
• Providing participants with a variety of options to choose from.
• Promoting competence by practicing skills and increasing knowledge.
• Avoiding the use of external rewards.

The participants in the comparison group received a general health education curriculum, based on various three to six week long educational topics such as preventive nutrition and effective communication skills.

Assessments took place at baseline, 4, 12, 16, 24, and 36 months. A variety of variables were measured: weight (rounded to the nearest 0.1 kg), demographics (such as age, education level, job or occupation), physical activity, diet, and physiological and psychosocial variables.

Currently, the study is ongoing, so there are no outcomes yet. Results from this study are expected to contribute to a better understanding of how motivational features, in particular the ones that relate to physical activity (exercise) influence treatment success during obesity treatment while exploring the utility of SDT in this context.