Projects

The rising prevalence of non-communicable diseases challenges health psychology research to find effective intervention strategies to change people´s health behaviors. It is particularly important to change eating behavior since this constitutes one of the most important preventive health behaviors. To facilitate eating behavior changes, new technologies such as smartphone applications (apps) are booming and are increasingly being considered in intervention development. App-based mobile interventions not only include a wide range of technical options along with the capability to reach a broad spectrum of the population, but also the possibility to intervene in real-life and real-time.

In order to use these advantages and open up new perspectives for changing eating behavior, the present dissertation aims to determine and quantify the potential of app-based mobile interventions for changing eating behavior by synthesizing the existing evidence. Moreover, deriving conclusions for future intervention development first requires a comprehensive understanding of eating behavior and its underlying psychological determinants as a necessary initial step towards changing it. For this purpose, the core determinants of daily eating behavior, including in-the-moment eating motives and eating happiness, are examined using an Ecological Momentary Assessment approach.

The first step of the present dissertation is to detemine the potential of app-based mobile interventions as an effective strategy for achieving changes in eating behavior in a large spectrum of the population. For this purpose, a systematic review and meta-analysis is conducted, including 41 studies and comprising 6,348 participants and 373 investigated outcomes. This shows that app-based mobile interventions are effective in changing eating behavior, including positive effects on fruit and vegetable intake. Moreover, positive changes in nutrition-related health outcomes such as obesity indices and clinical parameters are observed, showing small-to-moderate effect sizes. Overall, the present evidence confirm the high potential of app-based mobile interventions for health promotion, and can support both research and practice in further exploiting their full potential.

In a second and third step, the core psychological determinants of daily eating behavior are investigated by analyzing in-the-moment eating motives and eating happiness experienced in-the-moment to achieve a comprehensive understanding of the targeted behavior. In both studies, a smartphone-based Ecological Momentary Assessment is conducted over the course of a week to assess eating behavior, along with eating motives and eating happiness. Moreover, in addition to this real-life and real-time assessment approach, the present dissertation aims to point out new paths for data analysis, and a new visualization approach is introduced to handle the resulting high-dimensional data and allow an analysis at the between- and within-person levels. By combining the ecological valid assessment method with this comprehensive data analysis, the present dissertation gains considerable insight into the psychological determinants of daily eating behavior.

The investigation of eating motives as core motivators for daily food choices reveals differences between why people think they eat (dispositional assessment) and why they actually eat in the moment of consumption (in-the-moment assessment). In particular, visual appeal, liking, and pleasure show a high impact on in-the-moment eating behavior and can therefore contribute to the development of future app-based mobile interventions. Moreover, a more sophisticated analysis on the person and motive levels indicates considerably inter- and intra-individual differences, highlighting the importance of tailoring interventions not only to the individual but also to the situation.

Further, the investigation of eating happiness experienced in-the-moment as one important determinant of daily food choices indicates promising results for health promotion. Comparing eating happiness among different food categories reveals that healthy food choices such as fruits and vegetables evoke at least comparable to or even higher eating happiness than unhealthy food choices. Out of 14 different food categories, vegetable consumption contributes the largest proportion of total eating happiness, which indicates a ‘happy = healthy’ association. On the basis of these findings, it can be concluded that healthy food choices seem to also be happy food choices, and that the consumption of fruits and vegetables has both immediate and long-term beneficial psychological effects.

Bringing the present findings together, could pave the way towards a new approach in health promotion. By using in-the-moment interventions, eating happiness could be promoted as an important motivator that both drives human food choices and acts as an important cue for healthy eating. This might constitute an innovative intervention strategy that not only triggers healthy but also happy eating behaviors and enables the focus to be shifted towards a more positive and wellbeing-centered perspective on eating behavior.

An affective experience exists in different states - what we forecast the experience to be, what we experience in the actual moment, and what we remember having experienced. However, neither forecasted nor remembered experience is an exact copy of the in-the-moment experience. A great number of studies across various populations and settings has shown that both forecasted and retrospectively remembered experiences tend to be too extreme and systematically biased compared to the actual in-the-moment experience (‘impact bias‘). Most research has examined biases and the resulting divergences between states of experience for outstanding and rather confined events, such as a vacation experiences or medical treatments. The present dissertation expands on this research by focusing on repeated, familiar experiences of daily life, taking eating happiness as an example to enhance the generalizability of the divergence of both forecasts and retrospections compared to in-the-moment experiences. The differentiation between outstanding and repeated day-to-day experiences is important since in the latter case, people have individual past experiences that they can rely on.

In a first step, the correspondence between eating happiness as experienced in the moment and forecasted as well as retrospective eating happiness was examined in a real-life setting, taking the entire food intake of participants into account. Comparing eating happiness experienced in the moment to forecasted eating happiness revealed the prevalence of a considerable discrepancy whose magnitude was affected by both person-specific differences such as dispositional expectations towards eating (‘foodiness’) and experience-specific aspects such as the variability of the in-the-moment experience. More specifically, people with a low tendency towards foodiness displayed not only more variability in their in-the-moment experiences but also a greater discrepancy between forecasted and in-the-moment experiences compared to people with a high tendency towards foodiness. However, no interaction was revealed between dispositional expectation and variability of in-the-moment experiences regarding forecasting accuracy, indicating that the variability of the in-the-moment experience impacts the accuracy of forecasts equally across all participants.

Furthermore, retrospective eating happiness as manifested in the general belief that unhealthy foods are tasty, was compared to eating happiness experienced in the moment. The results across food categories and meal types indicated that the general belief does not represent the actual in-the-moment experience correctly. Specifically, the consumption of healthy choices such as fruits and vegetables and stereotypically unhealthy choices such as sweets and pastries evoked comparable eating happiness in the moment of consumption. In addition, analyses on the meal level revealed comparable eating happiness for dinner and snacking.

The second step focused on the actual in-the-moment experience. The potential and effectiveness of mobile technologies such as smartphone apps that have the technical capability to counteract both biases in forecasts and retrospections by focusing on in-the-moment behavior and experiences was examined. More specifically, a systematic review and meta-analysis including 41 studies and 373 outcomes was conducted to examine the effectiveness of app-based mobile interventions that target nutrition behaviors and nutrition-related health outcomes. The results indicated a positive effect of app-based mobile interventions for changing both nutrition behaviors and nutrition-related health outcomes, including obesity indices and blood parameters. In addition, moderator analysis including study design, type of app, sample, and intervention characteristics, did not reveal significant effects, which underlines the potential of interventions that use an in-the-moment approach.

Discussing the findings of the present dissertation, benefits and trade-offs regarding the assessment of different states of an affective experience are displayed. Furthermore, the validity of forecasted, in-the-moment and retrospective experience regarding different life domains and research aims is discussed along with the implications and functions of overestimations in forecasts and retrospective evaluations. Following this, the potential and opportunities of smartphone apps not only to change behaviors and related outcomes but also to increase learning from past experiences are illustrated, demonstrating a possibility to improve the correspondence between forecasted, retrospective and in-the-moment experiences.