Eline Roordink

General introduction
Overweight and obesity have emerged as a growing public health concern, with global rates steadily rising over the past decades. In the Netherlands, 50% of the adult population are overweight, with 14% classified as obese. This is problematic as being overweight is associated with an increased risk of various non-communicable diseases, such as cardiovascular diseases, diabetes, musculoskeletal disorders, and several cancers. Moreover, even in the absence of non-communicable diseases, being overweight is related to a reduced quality of life. While losing weight offers numerous health benefits for individuals who are overweight or obese, maintaining weight loss is often challenging.

Weight loss can be achieved by modifying both energy intake through dietary behavior, and energy expenditure through physical activity behavior. Behavior change maintenance is likely if the newly adopted behavior has become the default behavior in several situations and contexts. However, individuals often encounter circumstances where previous unhealthy behaviors resurface, leading to a lapse: a temporary slip-up or setback to old habits. If this initial lapse is followed by a series of lapses, a relapse may occur: a complete return to old unhealthy habits and behaviors. Understanding the predictors of lapse and subsequent relapse is crucial for preventing or minimizing their occurrence in weight loss maintenance behaviors.

After a general introduction, Chapter 1 describes the overall aim of this thesis. The overall aim of this thesis is to determine the predictors of lapse and relapse in weight loss maintenance behaviors, in specific physical activity and dietary behavior.

The specific sub-aims for this thesis are:

1. To synthesize the literature on the predictors of lapse and relapse in physical activity and dietary behavior, by applying a systematic search and review.

2. To identify predictors of relapse in physical activity and dietary behavior, from the perspectives of health practitioners who coach individuals during their weight loss process and the perspectives of individuals who have experienced relapse themselves.

3. To identify individual and environmental predictors of lapse in physical activity and/or dietary behavior, using ecological momentary assessment (EMA) amongst adults trying to lose weight.

Main findings

Chapter 2 describes a comprehensive review of the literature on predictors of lapse and relapse in physical activity and dietary behavior, using a systematic search and a narrative synthesis approach on prospective studies. The synthesis, which included 37 articles, identified self-efficacy as the only consistent predictor across various outcomes. Self-efficacy was found to predict both lapse and relapse in physical activity, as well as relapse in dietary behavior. Although some predictors showed enough data to support their relationship, the review revealed that many predictors were not sufficiently examined to provide conclusive evidence. In fact, several predictors were studied only once or had inconclusive findings. The overall quality of the included articles was also deemed low, with only 27% of them scoring high on the quality assessment (≥ 75%). Based on these findings, the literature review emphasized the need for more high-quality research to draw more substantiated conclusions.

Chapter 3 describes a concept mapping study to explore the perspectives of key stakeholders on predictors of relapse in physical activity and dietary behavior, and potentially identify new predictors of relapse beyond existing knowledge. Data was collected through concept mapping, which combines qualitative and quantitative methods to integrate group thoughts and perspectives. Eight concept mapping sessions were conducted with two stakeholder groups: health practitioners involved in coaching individuals during weight loss (N=39; five groups) and individuals who had experienced relapse themselves (N=21; three groups). A total of 43 predictors were identified. While many predictors were mentioned by both stakeholder groups, they differed in their views on the importance of these predictors in predicting relapse. Additionally, certain predictors were mentioned exclusively by one group. These discrepancies in stakeholder opinions provide an opportunity to enhance lifestyle coaching by increasing awareness of these variations and incorporating both perspectives during coaching sessions.

Chapter 4 describes an EMA study to examine predictors of lapse in exercise and dietary behavior, including positive and negative emotional states, perceived hunger, perceived stress, coping self-efficacy, and recovery self-efficacy. Potential differences and similarities between the predictors of lapse in physical activity and dietary behavior were also explored. The study involved 81 Dutch adults attempting to lose weight who participated in two 7-day EMA weeks, receiving semi-random prompts six times a day. In exercise behavior, feeling hungry was associated with an increased risk of lapsing, while feeling relaxed, coping self-efficacy, and recovery self-efficacy were associated with a reduced risk of lapsing. Regarding dietary behavior, coping self-efficacy and recovery self-efficacy were associated with a reduced risk of lapsing. These findings underscored the significant role of coping self-efficacy and recovery self-efficacy in both exercise and dietary behavior lapses. Consequently, it is recommended that practitioners and intervention programs focused on promoting sustainable physical activity and dietary changes prioritize the enhancement of individuals' self-efficacy. Effective techniques such as coping planning and cognitive restructuring can be used to bolster self-efficacy.

Chapter 5 describes an EMA study, using the same dataset as Chapter 4, to further identify social environmental predictors of lapse in dietary behavior. Included predictors were social norms, social pressure, social support and presence of others. Findings revealed that injunctive norm, descriptive norm, and social pressure, all toward diverting from diet plans, predicted dietary lapse. Social support toward sticking to diet plans and the presence of others did not predict lapse. Lapses predominantly occurred at home and gradually increased throughout the day. These findings suggest that intervention programs could benefit from also addressing social norms and social pressure. The involvement of partners or housemates could raise awareness about the impact of (unintentional) social pressure on the risk of lapsing and potentially reduce the level of exerted social pressure.

General discussion and conclusion

Chapter 6 summarizes and reflects on the main findings of the studies presented in this thesis. This thesis demonstrated that there are several predictors that show promise in predicting lapse and relapse, both at the individual level and within the environmental context. Across the studies, self-efficacy consistently emerged as a significant predictor, emphasizing its pivotal role in behavior change and relapse prevention. Additionally, the environment, encompassing both the physical and social environment, played a significant role. Particularly social pressure and social norms were key factors within the social environment.

Our findings underscore the multifaceted nature of predictors of lapse and relapse in physical activity and dietary behavior. This highlights the importance of addressing both individual and environmental factors for health practitioners guiding individuals toward sustainable lifestyle changes, and in interventions aimed at behavior change maintenance. Furthermore, to enhance lifestyle coaching, health practitioners need to be mindful that their perceptions of primary predictors of relapse in physical activity and dietary behavior might not fully align with those of individuals who have experienced relapse.

Moving forward, achieving consensus on operational definitions of lapse and relapse in physical activity and dietary behavior is of importance to advance future research in this field.