Research

Nudging healthy and sustainable food choices: three randomized controlled field experiments using a vegetarian lunch-default

Study: A randomized controlled trial was conducted at three conferences. Participants who registered for the conference online were randomized into two groups. One received a standard lunch registration with a non-vegetarian buffet as the default, with the option to opt into a vegetarian lunch. The other group received a registration with a vegetarian buffet as the default, with the option to opt into a meat lunch.

Findings: Changing the default meal option on a registration form from meat to vegetarian increased the vegetarian option on average from 7% to 87%, without pushback from the attendees.

Meta-analysis of the impacts of defaults on meat reduction

Study: A systematic review of twelve studies utilizing default interventions to reduce meat consumption

Findings: Defaults substantially decrease consumers' meat consumption, with 53% to 87% fewer options chosen across these studies.

Plant-based default nudges effectively increase the sustainability of catered meals on college campuses: Three randomized controlled trials

Study: Researchers investigated the effects of changing the default meal option from meat to plant-based at catered events on college campuses.

Findings: Participants assigned to the plant-based default rather than the meat default were over 3 and a half times more likely to choose plant-based meals. Implementing plant-based default menu options resulted in significant reductions in greenhouse gas emissions, land use, nitrogen, and phosphorus footprint, highlighting the potential to decrease the environmental impact while maintaining participant choice.

Nudging à la carte: a field experiment on climate-friendly food choice

Study: A randomized controlled experiment was conducted at a restaurant in Sweden. Customers in the control group were given a menu listing a meat and fish option, with a note that a vegetarian option was available upon request. Customers in the experimental group were given a menu listing a vegetarian and fish option, with a note that a meat option was available upon request.

Findings: The vegetarian and fish menu resulted in a 75% increase in sales of the vegetarian option, and a 56% decrease in sales of the meat option among customers in the experimental group, compared to the control group who received the meat and fish menu.

Motivating Sustainable Food Choices: The Role of Nudges, Value Orientation, and Information Provision

Study: Students were presented with a variety of printed menus and asked to select which dish they would order, though participants did not actually receive a food item. In the “default” condition, the menu they were handed contained only vegetarian options, and they were informed they could also order from a printed menu posted on the wall that contained meat options. In the control condition, the menu contained a mix of vegetarian and meat items.

Findings: In the default menu group, 92.5% and 89.7% of students chose vegetarian options, while only 47.4% and 40% of students in the control group chose vegetarian options.

Meat on the menu? How the menu structure can stimulate vegetarian choices in restaurants

Study: Participants were presented with menus that were vegetarian by default with the option to add meat, menus with a large number of vegetarian options explaining the benefits of vegetarian food, and menus with a large number of vegetarian options that did not explain the benefits of vegetarian food, then asked which dish they would order from the menu, though participants did not actually receive a food item

Findings: The strongest effect was observed with the default vegetarian menu with the option to add meat, which led to the most vegetarian dishes chosen (73% versus 44% and 61%, respectively).

A reversal of defaults: Implementing a menu-based default nudge to promote out-of-home consumer adoption of plant-based meat alternatives

Study: A field experiment in a Danish restaurant examined the change in diner choice when a “Menu of the Month” featured a meat-based special with a note that a plant-based special was available on request, versus when the special was plant-based and noted that a meat-based special was available upon request.

Findings: Among customers who ordered from the “Menu of the Month,” only 8.6% ordered plant-based when a meat-based special was the default, whereas 80% chose the plant-based special when it was the default.

Application of optimal defaults to increase selection of sustainable menu choices

Study: In a college dining hall field study, researchers examined the impact of presenting plant-based default, meat-based default, and free array (no default) menus on the selection of plant-based meals.

Findings: 71% of participants offered a plant-based default menu chose plant-based meals as opposed to only 10% of students who chose plant-based meals when offered a free array menu, marking an over 7 fold increase in the likelihood of choosing a plant-based entree from an plant-based default menu over a free array menu.

Can you default to vegan? Plant-based defaults to change dining practices on college campuses

Study: Researchers examined the effect of plant-based defaults at one dining station in an all you care to eat environment. This was a three-month field experiment conducted in campus cafeterias at three different universities. Each day, locations were randomly assigned to either a plant-based default or control condition. In the control condition, a meat-based and plant-based dish were offered side by side with no explicit default. In the plant-based default condition, only the plant-based dish was visible to diners at the station and listed first on the menu, while the meat dish was listed as available "upon request" and was placed outside of the diner’s view.

Findings: During the intervention period, a total of 15,278 meal servings were recorded. On days with a plant-based default, there was a 58.3% increase in the number of plant-based dishes served and a 57.2% decrease in the number of meat dishes served compared to control days.

Changing the default meal option at university events to reduce harmful environmental impacts: Six randomized controlled trials

Study: A randomized controlled trial was conducted at six university events across four academic institutions to investigate the effects of changing the default meal option from meat to plant-based at catered events.

Findings: Changing the default meal option on the RSVP form from a meal containing meat to a plant-based meal increased the selection of the plant-based option by 43 percentage points, reducing harmful environmental impacts by 45% while preserving participant choice.

Impact of increasing vegetarian availability on meal selection and sales in cafeterias

Study: Researchers collected observational data from two University of Cambridge college cafeterias to evaluate the association between the availability of vegetarian options and the number of vegetarian meals purchased during the spring, summer, and autumn academic terms. Researchers also conducted an experimental study to measure changes in sales of vegetarian options at a separate cafeteria, where vegetarian availability was increased from 1 in 4 to 2 in 4 options.

Findings: In this observational study, sales of vegetarian meals at the first and second cafeterias were 62% higher and 79% higher, respectively, when 2 in 4 options were vegetarian compared to when 1 in 4 options were vegetarian. In the experimental study, increasing vegetarian availability from 1 in 4 to 2 in 4 meal options increased sales of vegetarian meals by 41%. When reviewing the purchasing history of diners in the experimental study, those who were less likely to select vegetarian meals prior to the study were found to be most affected by the change in vegetarian availability.

Impact of increasing the relative availability of meat-free options on food selection: two natural field experiments and an online randomized trial

Study: Researchers conducted a series of experiments examining the impact of altering the ratio of meat-free meals.

Findings: When three out of four meal options were meat-based, 12% chose the plant-based option. Whereas, when three of four meal options were vegetarian, 48% chose the vegetarian meal.

Effects of increasing the availability of vegetarian options on main meal choices, meal offer satisfaction and liking: a pre-post analysis in a French university cafeteria

Study: A controlled trial was conducted at a French university cafeteria. During the control period, 24% of main meals offered were vegetarian. This was increased to 48% during the intervention period, with no other menu changes. Students were not made aware of the change.

Findings: Student satisfaction was evaluated through daily paper ballots (n = 18,342). Analysis indicated that doubling the availability of vegetarian main meals led to a twofold increase in their selection. Student satisfaction with the meal offer and liking of their chosen meal also slightly improved during the intervention period. Only 6% of students noticed the change in vegetarian meal availability.

Nudge to Nobesity I: Minor Changes in Accessibility Decrease Food Intake

Study: The study tested how the accessibility of certain food options relates to food intake in a buffet setting. Accessibility was operationalized by making certain options more difficult to reach by changing their location in the buffet line and by changing the serving utensil (spoon or tongs).

Findings: Making a food option harder to reach (by being placed in the middle of the buffet, as opposed to the edge) created a modest but noticeable change in how likely it was to be picked. Also, all food ingredients were consumed at lower rates when served with a pair of tongs as opposed to a spoon.

Comparison of three nudge interventions (priming, default option, and perceived variety to promote vegetable consumption in a self-service buffet setting

Study: This peer-reviewed study analyzed the effects of priming, defaults, and perceived variety on vegetable consumption in a self-service buffet setting. They used these three conditions to change the layout of the food, which included rice, chili con carne, white salad and red salad.

Findings: The default condition successfully increased vegetable consumption and decreased meat consumption compared to the control.

Increasing fruit and vegetable intake among male university students in an ad libitum buffet setting

Study: The experiment tested whether altering the serving sequence of healthier food options (fruits and vegetables) and serving them in separate bowls in a buffet setting impacted the quantity of foods selected by participants.

Findings: Serving fruits and vegetables first and serving them in separate bowls increased the quantity of fruits and vegetables selected, and decreased the quantity of animal-based foods selected.

Nudge the Lunch: A Field Experiment Testing Menu-Primacy Effects on Lunch Choices

Study: A field experiment conducted at a university cafeteria examined the relationship between placement at the top of the menu and share of items sold.

Findings: Placing a vegetarian option instead of a meat option at the top of a menu decreases the share of meat dishes sold by 11%.

Menu Position Influences Food Choice

Study: Servers at a Tel Aviv restaurant collected data on which option customers chose among two different menus. The only difference between the two was the placement of the items on the menu (i.e., beginning, middle, end).

Findings: Items were more likely to be ordered when they were listed first or last in a section, rather than in the middle.

Don’t Put Vegetables in the Corner

Study: A study by the London School of Economics and WRI Better Buying Lab examined the impact of segregating vegetarian dishes into their own section on a menu, versus integrating them throughout the menu.

Findings: Diners were 56% less likely to order a vegetarian dish when they were segregated into a special “vegetarian” section of the menu.

Increasing Vegetable Intake by Emphasizing Tasty and Enjoyable Attributes

Study: This experiment compared vegetable purchases with taste-focused and health-focused labels, as well as a basic control label, in five university dining halls over 130,000 meals.

Findings: Taste-focused labels increased vegetable selection by 29% when compared to the health-focused labels and by 14% when compared to the basic labels in a cafeteria setting.

Smart food policy for healthy food labeling

Study: Four field studies across different dining settings were conducted to test whether taste-focused labels encouraged more purchases of healthy items, sustained purchases over time, and improved attitudes toward healthy food options.

Findings: Taste-focused labels increased consumer choice of healthy food options and led to a durable increase in vegetarian purchases; health-focused labels led to a 45.1% decrease. Taste-focused labels also improved attitudes toward healthy foods.

The Language of Sustainable Diets: A Field Study Exploring the Impact of Renaming Vegetarian Dishes on U.K. Café Menus

Study: World Resources Institute’s Better Buying Lab partnered with Sainsbury’s cafes to investigate whether naming that emphasized taste and provenance would increase sales compared to naming that emphasized the lack of meat.

Findings: Renaming “Meat-Free Sausages and Mash” to “Cumberland Spiced Veggie Sausages and Mash” increased sales by 76%.

It’s All in a Name: How to Boost Sales of Plant-Based Items

Study: Panera conducted a month-long trial at 18 locations in Los Angeles during which they switched the name of their “Vegetarian Low-Fat Black Bean Soup” to “Cuban Black Bean Soup".”

Findings: Sales of the black bean soup increased 13% in those locations.

A matter of identity: Promoting plant-based food among meat-eaters through a common identity priming

Study: This study explored how social identity impacts meat-eaters' willingness to buy plant-based foods across four studies. Participants were exposed to advertisements or product packaging featuring a spokesperson associated with either a "common" identity (e.g., 'fun lover' or 'Gen Z') or a "vegan" identity.

Findings: Associating plant-based food with common identities, rather than a vegan identity, reduced meat-eater identity threat and increased their willingness to buy plant-based products.