Discussion
SAID, SHOP
This study examined the impact of calorie labelling and proportional pricing in a virtual online food delivery platform on portion size choice, kcals ordered and hypothetical spend from beverage, sandwich and fast food outlets. Compared to non-labelling conditions, calorie labelling had no significant impact on portion size selection of food or beverages from the coffee shop, sandwich shop, fast food outlet or when data were combined across all three outlet types. Calorie labelling did however significantly reduce total energy ordered in the coffee shop (-18.95kcals) and fast food outlet (-54.19kcals), but not significantly from the sandwich outlet (-0.43kcals). When data across outlets were combined, there was a small overall main effect of calorie labelling on energy ordered. For the fast food outlet only, calorie labelling was associated with a reduced total spend and in pooled analyses across the three outlets there was no difference in total spend based on calorie labelling condition. Presenting food and beverage items with proportional pricing (as opposed to standard value pricing) was associated with a decreased likelihood of choosing a larger beverage size from the coffee shop outlet by 42%. This statistically significant decrease was not found for the sandwich shop (21% reduction) or fast food outlet (7% reduction). However, when data were combined across outlets, there was an overall effect of proportional pricing, whereby presence of proportional pricing was associated with the participant selecting the larger portion size 0.2 times less (out of a possible 0–3 times) on average across the three outlets (a 7% reduction in number of times large portion size was chosen). Unexpectedly participants in the proportional pricing condition had a significantly higher total energy content of orders for the fast food outlet, as opposed to small non-significant decreases in the other two outlets. In all three outlets, proportional pricing was associated with increased hypothetical spend, and likewise a main effect of pricing condition was observed for combined outlets. No consistent interactions between a range of participant characteristics and interventions were identified across the different outlet types. Nor did we find any evidence that the effect of calorie labelling differed as a function of pricing condition for any of the outcomes.There was no evidence that calorie labelling had an effect on portion size selection of food or beverages across any outlet, but consistent with some research examining hypothetical food choice, labelling was associated with reductions in energy ordered [The majority of participants were supportive of calorie label interventions in the out-of-home food sector, which is consistent with findings from others studies [In proportional pricing conditions vs. standard value pricing, when data across outlets were combined, participants overall selected a larger portion size less frequently. For the separate outlets, this relationship was only significant for beverage purchases from the coffee shop. The same trends were observed for the sandwich shop (-21%) and fast food outlet (-7%) although differences were not statistically significant. It may be that a larger impact would be observed if a smaller size was offered for a proportionately lower price. In this study, participants were only able to choose between medium and large portion sizes. Previous research has found that increasing the number of options at the larger end of the scale (i.e., adding an extra-large option to small, medium, large) increased the number of people opting for the large size [Proportional pricing was associated with small non-significant decreases in total energy ordered in the coffee shop and sandwich outlets, but an unexpected increase in the fast food outlet. Exploratory analyses revealed that proportional pricing was associated with increased ordering of optional additional side dishes. In the study, proportional pricing was not presented for all side dishes (due to there being only one size) and many of the additional sides were low in price. Therefore, the effect of proportional pricing on total energy ordered may reflect lower priced items being perceived as better value for money when relative prices of larger meals increased (due to proportional pricing). Previous research has shown that many people rate the financial value of food products over factors such as nutritional content [In all three food outlets, proportional pricing was significantly associated with increased spend, showing that larger options are still attractive to many consumers even when more expensive. Although participants were broadly in support of proportional pricing (> 60%), across all three outlets, 90% of participants said that orders were typical for them (in terms of content and size). The lack of consistent effects of proportional pricing in the present study indicate that other complementary approaches, such as reformulation of existing food products, will be valuable in the out of home food sector [In the present study, we found a small increased spend in individuals with a greater BMI in proportional pricing conditions (relative to value pricing) for two of the three outlets, but no interactions with kcals ordered. There was also a small amount of inconsistent evidence that calorie labelling may exert a slightly stronger effect on kcals ordered among participants higher in weight control motives. Given the overall lack of convincing evidence across outcomes for moderation of calorie labelling or proportional pricing on outcomes by a range of participant level characteristics (including indicators of SEP) effects of these interventions may be largely similar across different sociodemographic groups. It is important to consider the role of habitual behaviour and preference in food purchasing. Specifically, it would be interesting to examine whether interventions such as those tested in the present study can override habitual behaviour and existing preferences, or whether intervention effects are limited to non-habitual choice and purchasing behaviours. Research suggests that when a behaviour is habitual, little information is required to make decisions, and individuals pay little attention to alternatives [