The PRECEDE model recommends that the causes of health problems be analyzed from multiple perspectives, taking into account multiple determinants of diet behavior; however, very few previous studies have focused on the efficacy of the PRECEDE model in regard to T2DM. Thus, the present study is somewhat unique, as it applied the PRECEDE framework to test factors associated with the diet behaviors of individuals with T2DM. Our findings suggest that predisposing, enabling, and reinforcing factors are crucial for understanding and promoting diet behavior practices. In addition, we determined that diet self-efficacy mediates the association between social support and diet behavior; in other words, such a change in behavior requires both internal and external factors. The results also indicated that individuals with high levels of social-support barriers tend to have low levels of diet self-efficacy, which in turn can lead to poor diet behavior.
Inducing factors are the factors that urge people to take necessary actions. Predisposing factors are factors that establish incentives to take a required behavior. In this study, predisposing factors specifically relate to diet self-efficacy. In the case of diabetes self-management, self-efficacy relates to a patient’s confidence in his or her ability to perform a variety of diabetes self-management behaviors.
Self-efficacy has two basic elements: efficacy expectations (self-efficacy) and outcome expectations. Efficacy expectation refers to the confidence of individuals in their own behavioral ability and their confidence in their ability to overcome obstacles to achieve a certain goal. Outcome expectation refers to the belief of individuals that they will obtain a positive health outcome by performing a specific behavior. Therefore, despite the obstacles in diet self-management, individuals with high levels of perceived diet self-efficacy will still attempt to achieve specific goals. The current results reflect the positive impact of this model on predisposing factors (diet self-efficacy), which is consistent with previous studies that have found that it is a useful predictor of enhanced diabetes self-management.
Enabling factors contain the facilities and skills needed to change a behavior, while reinforcing factors increase the possibility of the continuation of the recommended behavior. In this model, social support represents both the enabling factors and reinforcing factors. However, different from prior studies, it has produced a wide range of assessments of social support, discussing the utilization of medical personnel, family and friends, self-regulation, neighborhood communities, social organizations, media policy, and work environments. The results of our study demonstrate that social support plays a significant role in influencing, either directly or indirectly, changes in diet behavior.
Firstly, social support was found to be significantly and directly associated with increased diet-promoting behaviors. For instance, friends, family, and supporters of patients may provide information and tangible forms of support, and may set an example for healthy habits, thereby increasing the diet-promoting behaviors. Moreover, social support might have an emphasized role in terms of diet promotion, since individuals with diabetes can feel empowered when in a supportive social environment, which in turn could encourage them to engage in diet-promoting behaviors. Thus, for patients with diabetes, social support can constitute a fundamental approach to maintain self-management behaviors and overcoming barriers.
Furthermore, there are several possible explanations for the mediating role diet self-efficacy plays in the relationship between social support and diet self-management for diabetes patients. Self-efficacy is impacted by personal factors (i.e., age, education level) and environmental factors (i.e., barriers to behavior changes, social support). Further, King et al. showed that self-efficacy was strongly associated with behavior-specific support from family, friends, and communities. Venkataraman et al. found that positive family support increases peoples’ confidence in their ability to manage diabetes. Another important finding is that, according to previous systematic reviews, the effectiveness of diabetes self-management programs is strongly associated with their duration, and the effectiveness may gradually disappear after the interventions end[36, 37]. Similarly, many studies have indicated that self-efficacy may be successful when initiating behavioral changes, but it has also been suggested that these changes may not be maintained in the long-term. Thus, continued social support is key for long-term maintenance of self-efficacy. If diabetes patients are to persist in diet self-management, social support may further strengthen the impact of dietary interventions, and social support may therefore help to promote enduring behavior change. Some previous studies that have examined dietary interventions, but have not found significant improvements in their participants’ diet behaviors. However, many of these interventions concerned relatively intensive programs, and the course formats were rigid. Moreover, there has been some controversy suggesting that high-intensity education can lead to increased time and labor costs, increased feelings of burden, and subsequent negative effects on diet adherence. Thus, a program with a rigid format may harm participants’ confidence and increase long-term dropout rates.
This study has a number of strengths and weaknesses. The major strengths of this study are that it considers, based on the PRECEDE model, both internal and external factors that affect the diet self-management of T2DM patients. In addition, it is the first study to focus specifically on diet self-management. Furthermore, our research, for the first time, validates the role diet self-efficacy plays in the association between social support and diet self-management. Nevertheless, there are also several limitations to this study.
Firstly, this study was a cross-sectional investigation. Therefore, despite the hypothetical mediation model has a theoretical basis, it was not possible to draw firm conclusions about the directionality of the relationships between the study variables. Thus, longitudinal studies should be conducted to further understand the mediation model proposed in this study. Secondly, social support, diet self-efficacy and diet self-management behaviors were evaluated by self-report. So, these responses may be biased. However, this method is the only known feasible and cost-effective way to collect such data. Finally, we were unable to assign the participants randomly to the study; the respondents were selected by telephone follow-up. This means that the findings are probably not generalizable to all individuals with diabetes and should be interpreted as such. As a consequence, the application of cluster randomization was also not possible.