Worldwide, overweight and obesity have become a major public health problem as they constitute a considerable risk for many chronic diseases such as certain cancers, type 2 diabetes and coronary heart diseases
[1, 2]. Consequently, effective public health strategies are urgently needed to prevent overweight and obesity and reduce the burden of disease
. A high intake of energy dense foods has been associated with excess weight gain
. Over the past decades, the number of snacking occasions per day and energy density of snacks have increased substantially
As empirical evidence for the strong environmental influence on overeating and excess weight gain is growing
, environmental approaches are increasingly being advocated as offering important potential for improving eating habits. Consumers make their decisions in an environment in which many cues may influence their purchase, although they are often not aware of this influence. Increasingly, efforts are being done to reshape the environment in which consumers make their food decisions
. Recently, the concept of nudging has become very popular in this respect
. Nudging works from the setting in which a choice is presented and aims to make beneficial choices (from a consumers’ perspective) more appealing
. They can be seen as relatively simple, easy to implement and inexpensive interventions. A key characteristic of nudging is that consumers maintain their liberty of choice
. This implies that interventions do not ban ‘forbidden’ products or enforce consumers to make a particular choice.
The present study examines the possibility of nudging consumers towards healthier snack choices near the checkout counter by altering the accessibility and availability of both healthy and unhealthy snacks. Both availability and easy accessibility of energy dense foods have been identified as risk factors for overeating
. In food studies, availability and accessibility has been conceptualized in various ways, such as spatial accessibility and means of transportation to stores
. Both of them have been recognized as promising starting points to design effective intervention tools. Interventions based on these features have typically been studied separately or combined with other interventions such as price alterations or labelling. For example, results from an intervention at a large hospital cafeteria suggest that a color-coded labelling intervention in combination with a rearrangement of healthy items (displaying them at eye level) can contribute to increased sales of these items
. In another study, accessibility of (un)healthy foods and the provision of caloric information were manipulated on paper menus distributed at a fast food sandwich chain. It was found that participants were more likely to choose low-calorie options when these were put front-page rather than presented at the back page of the menu
. Hanks and colleagues
 showed that adding a convenience line displaying only healthy foods in a school lunch room increased sales of healthier food by 18% and decreased sales of less healthy foods by nearly 28%. Maas and colleagues
 manipulated accessibility by changing distance to unhealthy snacks in a lab study. They found that putting snacks further away reduced the likelihood and amount of snack intake. Similarly, making a food slightly more difficult to reach reduced intake of salad bar food by 8-16%
. Not all studies find such strong effects, probably because of strong existing preferences for particular products
. For example, Meyers and colleagues
 manipulated the accessibility of high- and low-calorie desserts in a hospital cafeteria. Making low-calorie desserts less accessible decreased the likelihood of their selection and resulted in fewer desserts taken at all. However, when high-calorie desserts were made less accessible and visually salient, people accepted the inconvenience of reaching for them rather than eating a low calorie dessert. In sum, the few experimental studies that have explored accessibility provide promising but sometimes inconclusive results, probably due to different type of manipulations and settings (i.e. lab environment, school, hospital canteen, fast food chain).
Besides manipulating accessibility or convenience, studies manipulating availability typically origin in the marketing field
[19, 20]. For example, although this study was conducted almost four decades ago, Curhan
 showed that doubling shelf space for hard fruit in a supermarket increased sales by 44%. In a more recent study on vending machines in bus garages, the number of available healthy items was increased while at the same time prices of these items were lowered. Although the effect of lowering prices cannot be separated from the effect of increasing availability, the interventions resulted in 10-42% higher sales of healthy items
. All in all, previous studies particularly focused on the effects of accessibility, while availability has received less research attention in the field of public health promotion. In this study, accessibility is defined as the convenience or closeness of physically obtaining a product in a shelf space. We define availability as the presence of snacks ready for immediate choice by consumers.
No research to date combined both the effects of availability and accessibility to better understand their potential as a simple strategy to help people make healthier food choices in a worksite canteen. To inform new policy making in public health, the contribution of this paper is that we address the effect of availability on healthy food choices, both as a main effect and in combination with accessibility that has been studied more widely. Moreover, a lab study alone is not robust enough to provide reliable predictions about how people behave in a real-life context. Therefore, we address these effects both at the fundamental level (controlled lab experiment) as well as at the public health implication level (a realistic real life setting).
Research in the field of behavioural economics has shown that consumer decisions are often irrational and prone to biases
. Visitors of a self-service restaurant or canteen are often in a hurry and tend to be hungry, which makes them more prone to these biases. The interventions in our study aim to take advantage of biases related to easy accessibility and availability. Altering the ease of access to snacks basically means that it requires less effort to obtain them. People furthermore have the tendency to go for the default option as this typically requires the least effort due to habits or even ‘laziness’
. Availability can influence consumer choices in various ways. More healthy snacks present for purchase increases the likelihood that consumers find a snack that fits their need. Higher availability of healthy snacks leads to a larger assortment which tend to raise consumer expectations and satisfy consumers with a high need for variety
[19, 23]. By enlarging the available assortment of healthy snacks, we made these snacks the implicit default. This may function as a cue that implies a consumption norm. Typical checkout counter assortments including a variety of chocolate bars, candy and savoury snacks speak to the desire of immediate pleasure rather than uncertain rewards such as achieving a healthy body weight. Food products and snack displays are often designed to stimulate the automatic affective system of human behaviour, which is being driven by triggers in the environment. Therefore, our intervention aims to make taking a healthy snack slightly more convenient and attractive while preserving freedom of choice.
Recently, ethical concerns have been raised that nudges could be too intrusive and restrict (perceived) freedom of choice
[24, 25]. For example, strategies that focus on offering people a default option are problematic if people tend to overlook the possibility to make alternative choices
. Moreover, according to reactance theory
, eliminating choice options or putting pressure on people to eat healthy may lead to reactance in that some consumers will do exactly the opposite (e.g. go for the unhealthy option). Therefore, an additional aim of this study is that we also examined participants’ perception of their freedom in making choices and choice satisfaction.
The first study reported provides a lab experiment into whether shelf arrangement (location of healthy snacks on top versus bottom of shelf display) and assortment structure (assortment includes either 75% or 25% healthy snacks) influences the type of choices consumers make. Pictures of shelf displays were created to simulate snack food displays that can typically be found near the checkout counter of self-service restaurants or canteens. Because this study was conducted with tightly controlled stimulus material in an imaginative choice situation, the question is whether the results would generalize to a ‘real-world’ snack choice situation. Therefore, the second study is a field experiment in which the same manipulations were applied to an actual snack shelf display in a hospital canteen. Worksite restaurants are important intervention sites because of trend towards increasing out-of-home consumptions
To summarize, changes in a snack assortment in terms of effort required to actually grab a product and the size of an assortment may make healthier snacks more salient, attractive, normative and convenient. For both studies, it was hypothesized that the individual and combined effect of increasing the availability of healthy snacks (while at the same time not banning unhealthy snacks) and positioning them at the top of the shelf display would increase sales of these healthy options. We manipulate the number of facings of healthy snacks and the vertical position of 16 snacks, while keeping total shelf space constant and retaining the availability of unhealthy options.
In sum, the objective of this article is to examine the effects and interplay between shelf arrangement and assortment structure on consumer choices for healthy and unhealthy snack products.