Research on plant-based defaults relies on behavioral nudges and choice architecture to influence dietary shifts. Based on a review of the evidence, we present this research overview addressing the effectiveness of plant-based nudge and default strategies.
As much as we might like to think otherwise, many of our daily decisions aren’t the result of purposeful thought or deep consideration, but choices that emerge from our habits, psychological biases, and social and physical environments. Nudge theory posits that by changing the choice architecture of our decisions, we can promote better behaviors at a large scale.
In practice, imagine moving all the healthy food to the front of your refrigerator (choice architecture) to increase the likelihood of reaching for an apple for your midnight snack rather than something you’re trying to avoid. That’s a nudge! This strategy has lots of advantages, but one big one is that it doesn’t remove choice itself (i.e., customers aren’t throwing away all of your junk food overnight), so it’s unlikely to cause much, if any, grumbling. This represents a powerful opportunity for a diet shift—in institutions, nudges can create sustainable dining at scale for every meal without significant consumer pushback.
Before we jump into the science, let’s define some key terms.
Nudge (or Plant-Based Nudge): As we use the term, a nudge is any subtle way of encouraging a consumer to choose a plant-based option. This can include the format of a menu, the physical space of a food service area, the phrases used by cafeteria staff or servers, and much more.
Plant-Based Defaults: The plant-based option is served as the default, with meat available upon request. This is done in various ways, such as cafeterias offering plant-based dishes with a sign indicating that meat and dairy are available by request, or a conference registration form asking people who opt for meat to check a box.
(Note: You may also have seen the term “DefaultVeg,” which is our university campus program.)
Climate-Friendly Ratios: Food service settings may increase the ratio of plant-based to meat options on a menu, as offering a greater variety of plant-based choices tends to lead diners to select fewer meat dishes.
Choice Architecture: This psychological term refers to the way choices are presented to people to guide their decisions. For example, when a grocery store places more profitable items at eye level and less profitable items near the floor, it structures consumer choice to its own advantage. In a dining setting, choice architecture can encompass menuing, cafeteria design, and food labels, among others, offering opportunities to incorporate nudges into the dining experience.
Menu Engineering: When engineering a menu, institutions can make the plant-based option more appealing by adjusting placement, descriptions, photos, and more. These are all specific examples of nudges.
Plant-based defaults often —but not always —depend on internal allies—people working in offices or cafeterias who want to be more sustainable and who may or may not follow a plant-based diet themselves. This represents a key advantage of the programs: they have widespread appeal, regardless of individual eating habits.
The research is unequivocal—this is a powerful strategy. Study after study after study shows that centering plant-based foods as the default is highly effective at reducing meat consumption and increasing plant-based food consumption without significant pushback.
But what about the long term? For example, if a student eats at a plant-based default university cafeteria for four years, are they more likely to reduce their meat consumption later in life? If so, plant-based defaults would have an even larger capacity to impact animals and the environment. At this point, we don’t know for sure—but nudges work, in part, because they influence social norms. Since social norms are critical to shaping and sustaining preferences for plant-based dining, some behavioral scientists believe defaults can lead to long-term dietary change. More study is needed.
When implementing nudges and defaults, it’s important to recognize that they are much more effective with specific demographics than others. Multiple studies have found that nudges work best for people who are already reducing their meat consumption (flexitarians or reducetarians) or people who are already environmentally or health-conscious. Nudges may also work better on women than men; this may just be because women are more likely to be flexitarian than men.
If a default isn’t possible for a given institution, other strategies can still influence meal selection. For instance, increasing the number of plant-based options on the menu without making them the default can be an effective strategy. In fact, doubling the number of plant-based meals can increase their selection from 41% to 79%, while increasing vegetarian options from 25% to 75% can increase their popularity from 12% to 48%. Improving the labels of plant-based meals (discussed in detail below) can also be somewhat effective in promoting individual menu items.
Given that not all stakeholders will be on board with a plant-based default, here is a handy chart to help determine which compromises are most ideal.
Since nudges can vary so much, let’s review some findings for some of the most common types of nudge-based situations.
Most Plant-Based Default programs take place in buffets, dining halls, office cafeterias, or similar food services, and most research on their effectiveness is conducted in conference or university dining halls.
Instituting a plant-based default option in dining halls (where meat was available but had to be specifically requested) was a success. Across several studies, as shown in the graph below, these programs massively increased the portion of veg meals ordered and eaten: of the well-executed defaults, the percentage of plant-based options jumped from an average of 17.2% to an average of 72.5%, or 55 percentage points—more than quadrupling the baseline percentage! While writing this overview, we were unable to find evidence of an appropriately implemented plant-based default program that failed to reduce meat consumption. In other words, this works.
A few notes: we excluded one study (the Rensselaer trial in the Food for Climate League Study) from this analysis because the default implementation was poor: inconsistent signage, prominently displayed meat options, and reports of servers guiding students toward meat rather than plant-based options. With this incorrect implementation, veg orders were ordered at baseline. Secondly, all of these studies were conducted in the U.S. or Europe, and we did not find any research on plant-based default programs in other regions—meaning we don’t yet know whether this effect would be the same elsewhere, particularly in the Global South.
Instituting a well-planned plant-based default saves money. According to an analysis of plant-based food options in New York City hospitals (conducted in collaboration with the Better Food Foundation), these options saved hospitals about .59 cents per meal by using whole-food plant-based ingredients.
Multiple studies confirm that using plant-based defaults significantly reduces food-related carbon emissions. One study at Tulane University, Lehigh University, and Rensselaer Polytechnic Institute found a reduction in food-related carbon emissions of about 23.6%; another analysis for the New York City Health and Hospitals resulted in a 36% reduction; and a third at UCLA and Harvard estimated it at 38.9-42.7%.
Aside from the bottom lines and carbon emissions reduction, these initiatives are often quite popular. In two reports—the New York hospital initiative and a set of experiments in Denmark—plant-based initiatives had an approval rating of 90%+ among diners. Internal data from students at cafes with plant-based defaults shows that only a small fraction disapprove — in one sample, just 1 out of 14. Another study found that across three universities, students’ enjoyment of the plant-based dish increased when it was made the default, surpassing even the meat dishes. And in an online study, participants’ interest in eating out at a restaurant didn’t significantly change when strong plant-based nudges and defaults were added to the menu.
Plant-based defaults help institutions meet climate and other sustainability goals, make their menus more inclusive to everyone—including the estimated 50% of the Latino and Hispanic community, 80% of African Americans and Native Americans, and more than 90% of Asian Americans who are lactose intolerant, as well as people from religions or cultures that restrict animals products—while improving institutional bottom lines and preserving diner satisfaction.
If you work at an institution, organization, or company that serves meals and want to get started, read for tips on how the plant-based defaults can be implemented effectively. For further information, visit the Behavioral Nudges Research List.
*evidence-based blogs or resources, not original research