Does dietary variability promote uncertainty about expected satiety?

The increased prevalence of obesity is widely attributed to a change in our dietary environment (e.g., increased availability of larger portion sizes and high energy-dense foods). In many industrialised countries there has been a dramatic increase in ‘dietary variability’ (specific types of food are now available in a wide range of flavours, brands, etc.). Often these varieties will differ considerably in their energy density. Studies in rodents have suggested that consuming a particular food in a variety of energy densities inhibits the acquisition of flavour-nutrient associations. In humans, meals are often planned in advance and then consumed in their entirety. An excellent predictor of meal size is the extent to which a food is expected to confer fullness. These ‘expected satiety’ judgments are influenced by prior experience with a food. For example, exposure to a wide variety of different pepperoni pizzas is associated with a lower expected satiation for that food. Here, to build on this finding, we selected 10 foods that had high dietary variability. For each food and for each participant, we quantified exposure to the different varieties and we assessed expected satiety and ‘expected satiety confidence.’ We predicted that dietary variability generates uncertainty about the post-ingestive effects of a food and reduces expected satiety. This research represents an attempt to translate observations across species. Moreover, it has the potential to expose an important yet underexplored feature of our environment that might contribute to overeating and obesity.