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Theses Doctoral

The Theory of Planned Behavior as a Predictor of Adherence to Bariatric Recommendations for Diet and Physical Activity

Persaud, Amrita

Bariatric surgery has emerged as the most effective method for producing substantial long-term weight loss and inducing remission or reducing severity of many comorbidities for individuals with severe obesity. However, maintaining these successes from surgery requires that individuals combine the surgical intervention with numerous behavioral changes including dietary, physical activity, and lifestyle behaviors. Despite the positive weight and health outcomes associated with bariatric surgery, a proportion of the population experiences insufficient weight loss or weight regain, which may depend on the individual’s adherence to the bariatric behavioral recommendations. Few studies have investigated specific bariatric behaviors and whether they are impactful on weight outcomes.

The purpose of this study was to (1) examine the extent to which constructs of the extended Theory of Planned Behavior (TPB) predicted six bariatric behaviors: (a) eating protein at the start of a meal, (b) eating three to five daily servings of fruits and vegetables, (c) avoiding sweet foods, (d) avoiding salty snack foods, (e) avoiding sugar sweetened beverages, and (f) exercising for 30 minutes daily at moderate to vigorous intensity; (2) to evaluate the relationship of the aforementioned behaviors with excess weight loss outcomes; and (3) to explore the facilitators and barriers successful bariatric patients identify as factors that influence their adherence to bariatric dietary and exercise behaviors. A sequential explanatory mixed methods approach was used to address the purpose of this study. The first component consisted of collecting quantitative data from bariatric patients between 6-24 months post-operative while the second was completed by collecting qualitative data from participants, who based on certain criteria, were considered to be successful one year or more after their bariatric surgeries.

Quantitative component: A cross sectional design examined a convenience sample of 136 mainly female (89.7%) and Hispanic (72.1%) bariatric patients that underwent either a Roux-en-Y gastric bypass or sleeve gastrectomy in one ethnically diverse New York City hospital. Instruments for this study were developed based on previous research and translated into Spanish. Reliability estimates and content validity were assessed with a sample similar to that used in the study for both the English and Spanish instruments. The variables found in the extended TPB were assessed through instrument items that measure intention, attitudes, subjective norms, perceived behavioral control, anticipated behavioral outcomes, normative beliefs, control beliefs, and the additional constructs of anticipated emotions and self-identity in relation to the six bariatric behaviors. Adherence to bariatric behaviors was measured by a frequency instrument. Pre- and post-operative weight measures were obtained from participants’ electronic medical records. Multiple regressions were used to establish the predictors for each behavior.

For each behavior, attitudes towards the behavior contributed to the model for predicting behavioral intention. On the other hand, subjective norms were not found to be predictive for all behaviors with the exception of avoiding sweet foods. Behavioral intention for all behaviors was low and mainly non-significant, suggesting other constructs may be involved in order to adhere to the behavior.

The level of adherence to these six behaviors remained consistent over the 6 to 24 post-operative months. To note, participants were not adherent to fruit and vegetable consumption and physical activity recommendations.

Qualitative component: A purposeful sample of 11 bariatric patients that were considered successful based on study criteria participated in in-depth, semi-structured, individual interviews using a questionnaire developed from the main theoretical constructs of the TPB. In an effort to increase the understanding of the facilitators of and barriers to adherence, the addition of constructs found in the Health Action Process Approach framework were used to identitfy emerging themes. Content analysis of audio recording revealed (a) outcome expectations, (b) nutrition knowledge and skills, (c) social support, (d) attitudes towards adherence, (e) perceived behavioral control, (f) coping and planning strategies, and (g) recovery self-efficacy as major themes that influenced participants’ behaviors. A main facilitator to adhere to bariatric recommendations was outcome expectation, as post-operative patients saw the improvements in their health and quality of life following the bariatric surgery intervention as motivators to continue following recommendations and therefore preserve positive outcomes. At the same time, many participants stated difficulty in adhering to the recommendation of exercising at a moderate or vigorous intensity for 30 minutes on a daily basis.

Conclusion: Using a behavioral change theory provides a valuable framework for explaining adherence to healthy dietary and physical activity behaviors for bariatric patients. Nutrition education and behavioral interventions should focus on improving adherence to the recommendations of consuming fruits and vegetable and exercising daily, aiming to enhance attitudes towards these post bariatric surgery behaviors and addressing barriers to physical activity.


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More About This Work

Academic Units
Behavioral Nutrition
Thesis Advisors
Contento, Isobel R.
Ph.D., Columbia University
Published Here
June 5, 2019