The present dissertation addresses psychological influences on eating behavior.
Understanding why people eat what they eat in everyday life, that is, motives for eating behavior, is crucial for the development of interventions to promote normal eating and to prevent eating disorders. Furthermore, enhancing knowledge about both, individual and situational factors facilitating (pull factors) or impeding (push factors) healthy eating is essential for the prevention and treatment of obesity and its accompanying diseases. Accordingly, this dissertation encompassed three different goals. The first goal was to capture a wide range of motives underlying normal eating behavior and to develop on this basis a concise questionnaire, that is, the Eating Motivation Survey (TEMS). The second goal of this dissertation was to investigate the impact of these individual variables on dietary healthiness and the third goal was to examine the conjoint influence on eating behavior of both, individual and situational factors.
In a series of studies, in a first step motives were brought together from existing literature, interviews with practical working nutrition experts, and from structured expert discussions with health psychologists of the University of Konstanz. From this composition of 331 motives, we developed a preliminary version of the TEMS. In a second step, 1,250 participants filled in this questionnaire, yielding 13 motive factors in exploratory factor analysis. Based on these results, the preliminary TEMS was refined to 15 motive factors and tested in another sample of 1,040 participants in a third step. Confirmatory factor analyses yielded a satisfactory model fit for a full and a brief survey version. The motive factors were Liking, Habits, Need & Hunger, Health, Convenience, Pleasure, Traditional Eating, Natural Concerns, Sociability, Price, Visual Appeal, Weight Control, Affect Regulation, Social Norms, and Social Image, ordered according to the reported frequency of motives to trigger eating behavior. Factorial structure was generally invariant across gender and body mass index (BMI), which indicates a high stability for the Eating Motivation Survey scales. On the mean level, however, significant differences in motives for eating and food choice associated with gender, age, and BMI emerged. Interestingly, factorial correlations suggested that socio-cultural motives such as sociability, social norms, traditions, and social image concerns were highly related to each other. However, they were also related to biological motives like visual appeal and pleasure. In contrast, health concerns, which are typically promoted by public health interventions, were only related with the weight control motive and natural concerns. In order to trigger sustainable eating behavior changes, health concerns may need to be positively related to social and biological incentives for eating.
To examine the impact of these individual factors on eating behavior, that is, dietary healthiness, we exemplarily investigated the conjoint impact of the motive to eat to regulate negative affect, as a potential push factor, and the motive and capacity for weight control, as potential pull factors. In a cross-sectional survey study (N = 761 women) both, a high motive and capacity for body weight control predicted dietary healthiness independently, whereas a high affect regulation motive was associated with a more unhealthy dietary pattern. An optimal dietary pattern was only present in participants with both, a high motive and capacity for weight control. However, even these highly controlled women showed a decrease in healthy eating if they simultaneously had a high tendency to regulate negative affective states through eating. The most unhealthy dietary pattern was present in participants with low motive and capacity for weight control as well as a high motive to eat in response to negative emotions. Thus, in theory and practice it seems important to account for both, factors facilitating (pull factors) and impeding (push factors) healthy eating, when asking for influences on dietary healthiness.
Last, the conjoint impact of both, individual and situational influences on eating behavior was examined in an experimental setting. As situational influences we manipulated characteristics of the social situation. In contrast to previous research, focusing on stressful social situations, we focused on the effect of a positive social situation on eating behavior compared to a neutral and negative social situation. The effect of this situational manipulation was regarded in dependence of the individual motive to eat in response to stress. Manipulating the social situation, participants were either rejected by an ostensible second participant (social exclusion condition), or the experimenter delivered very positive feedback from this second participant (social inclusion condition). Social exclusion led participants with motive to eat in response to stress (stress eaters) to an increased consumption of ice cream in a subsequent ostensible taste test compared to participants without this motive (stress fasters). Social inclusion, however, reversed this pattern, causing stress fasters to eat significantly more ice cream than stress eaters. Hence, understanding the impact of the social situation on eating behavior requires accounting for people`s individual motives. Extending the situational perspective through the investigation of a positive social situation showed that individual variables, which have been discussed as pull factors in previous research (i.e., the tendency to eat less when stressed), can also act as push factors in dependence of situational variables.
In contrast to previous research, focusing on pathological and stress-related eating behavior, this dissertation addressed normal eating and the effect of positive situations. To account for the multiple factors, influencing eating behavior, this dissertation followed a comprehensive approach. This included bringing together multiple eating motives as well as the investigation of their conjoint impact on eating behavior, also in combination with situational variables. Choosing this comprehensive approach, we identified relations between eating motives, which may have implications for the development of interventions to promote health.
