As concerns about climate change and public health grow, institutions are looking for ways to encourage more sustainable eating habits. One effective strategy is default-based nudging, where plant-based meals are presented as the primary option, but people can request meat dishes if desired. Prior research has shown that default choices influence behavior across various settings, but little is known about their impact in all-you-care-to-eat university dining halls.

For the present study, researchers tested the effectiveness of plant-based defaults at three U.S. universities: Tulane University in Louisiana, Lehigh University in Pennsylvania, and Rensselaer Polytechnic Institute in New York. They aimed to determine whether this simple change could increase plant-based meal selection and reduce the environmental footprint of campus dining.

The study involved a randomized controlled trial conducted over five weeks. Each university dining hall had designated “Plant Default Days” and “Control Days.”

• On Plant Default Days, the plant-based dish was the only visible option at a serving station, with signage indicating that students could request the meat version.
• On Control Days, both plant-based and meat options were displayed side by side.

The researchers measured dish selection rates, student satisfaction, staff experiences, and environmental impact, analyzing over 15,000 meal choices across the three campuses.

The results showed that plant-based defaults significantly increased plant-based meal selection. On Control Days, only 27% of students chose a plant-based meal. On Plant Default Days, however, this number rose to 58% — more than double the usual rate. At Tulane and Lehigh, where implementation was more consistent, 81.5% of students selected plant-based meals when it was the default.

Greenhouse gas emissions from food were reduced by an average of 24%. By shifting more students toward plant-based options, total emissions from dining hall meals decreased, highlighting the environmental benefits of this approach.

Student satisfaction remained stable, with some preferring plant-based meals. Surveys revealed that students — including meat-eaters — were open to plant-based options. Plant-based meals received higher satisfaction ratings when served as the default compared to when they were simply offered as an alternative (an average score of 5.1 versus 4.4 on a seven-point satisfaction scale).

Dining hall staff found plant-based defaults easy to implement. Surveys and interviews indicated that staff enjoyed experimenting with new plant-based recipes. The intervention required minimal additional effort (an average score of 2.1 on a seven-point difficulty scale), and staff were interested in expanding plant-based offerings.

Despite these encouraging findings, social norms still favor meat consumption. Meat remained the dominant protein source for students, with 43% consuming meat seven or more times per week. However, this study revealed an opportunity for change. Students and staff expressed openness to reducing meat consumption, indicating that plant-based defaults could help shift long-term eating habits.

Challenges And Opportunities

While the intervention was successful overall, inconsistent implementation at Rensselaer reduced its effectiveness in that location. Visibility of meat dishes, lack of clear signage, and staff assumptions about student preferences undermined the default effect.

“Spillover effect” was also observed. Some students who visited the intervention stations on Control Days avoided them on Plant Default Days, leading to a 26% decrease in the overall number of all dishes served at these stations on Plant Default Days.

Thus, to maximize impact, universities should:

• Ensure proper implementation, with clear signage and hidden meat options;
• Provide culinary training to make plant-based dishes more appealing; and
• Pair defaults with social norm messaging and menu design strategies to further encourage plant-based choices.

Further studies could check whether similar results are obtained in other universities, as well as alternative settings such as schools, hospitals, and workplaces.

Implications

For animal advocates, this study demonstrates that plant-based defaults are a simple, effective way to encourage sustainable eating habits. When implemented correctly, they increase plant-based meal selection, reduce food-related emissions, and maintain student satisfaction — all with minimal disruption to dining operations. These findings have implications beyond universities, as similar strategies could be applied in corporate cafeterias, hospitals, and other institutional food settings.

By making plant-based meals the default, food service providers can take a low-cost, high-impact step toward a more sustainable food system.