In Chapter 2, I modelled the cost of healthy and current diets for an average Dutch household. On average, healthy diets were 24% more expensive than current diets and this difference increased by increasing educational level. The findings in Chapter 3 support those in Chapter 2 as I found that dietary cost partly explains socioeconomic inequalities in dietary quality measures. In Chapter 4, I investigated the mediating role of other diet-related material and psychosocial factors in the relation between SEP indicators and dietary quality. When combining the results from Chapters 3 and 4, I found that dietary cost as a material resource and cooking skills and resilience to the unhealthy food environment as psychosocial resources mediated around 30% of the association between SEP indicators and dietary quality. Food expenditure, perceptions of healthy food accessibility, healthfulness of the food retail environment, insensitivity to food cues and eating habits did not mediate this association. Thus, I concluded that diet-related material and psychosocial factors only partly explain socio-economic inequalities in dietary behaviours. Then, we developed a virtual supermarket in which nudging and pricing strategies were implemented to investigate the separate and combined effectiveness of these strategies on the proportion of healthy food purchases. As described in Chapter 6, a combination of different recruitment strategies led to the inclusion of 455 participants, of whom only a small proportion was truly low SEP. The virtual supermarket experiment showed that salient nudging strategies as well as pricing strategies alone did not lead to increases in healthy food purchases (Chapter 7). However, actively communicating these pricing strategies and combining these with nudges led to an approximately 3% increase in the proportion of healthy food purchases. The finding that nudging strategies alone may not be sufficient to increase healthy food purchases was confirmed in Chapter 5 where I investigated the effectiveness of on-shelf sugar labels on beverage sales within 41 randomly selected supermarkets. The results indicated that after the implementation of on-shelf sugar labels, the sales of targeted beverages did not change compared to comparison stores. The findings in Chapters 5 and 7 led me to conclude that it is important to combine several strategies and that nudging strategies alone may not be sufficient to increase healthy dietary behaviours. With regards to the possible differential effectiveness of nudging and pricing strategies, I investigated the modifying role of socio-economic indicators (Chapter 7) and other personal characteristics (Chapter 8) in the relation between nudging/pricing and healthy food purchases using the aforementioned virtual supermarket study. No evidence was found to suggest that nudging and pricing strategies in a supermarket setting work differently depending on individuals their SEP or personal characteristics. Using data from the aforementioned virtual supermarket study, I investigated in which food groups nudging and pricing strategies most effectively change product purchases and where potentially within-food group substitution or spill-over effects occur (Chapter 9). The results indicated that the largest effects were found for dairy and grains. These results suggest that dairy and grains may be the most promising food groups to target in order to achieve healthier food purchases in a Dutch setting. As little is known about within food group substitution and complementary behaviours, in Chapter 10, I used data from a New Zealand virtual supermarket study to investigate possible substitution and complementary effects of health-related taxes within food groups. As no consistent pattern of substitution of complementary purchasing was found, I was unable to conclude which food groups are best targeted by pricing strategies.
|Qualification||Doctor of Philosophy|
|Award date||17 Nov 2021|
|Place of Publication||Amsterdam|
|Publication status||Published - 17 Nov 2021|