Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining halls
Abstract Reducing meat consumption, especially in high-intake countries such as the United States, is crucial in mitigating the climate and biodiversity crises and improving public health and animal welfare. Choice-architecture interventions or nudges in the food domain, such as choice defaults (e.g...
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2025-04-01
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| Online Access: | https://doi.org/10.1186/s12889-025-22495-9 |
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| author | A. Voşki M. Braginsky A. Zhang J. Bertoldo S. Egan L. A. Levig M. Mueller Ihrig M. B. Mathur |
| author_facet | A. Voşki M. Braginsky A. Zhang J. Bertoldo S. Egan L. A. Levig M. Mueller Ihrig M. B. Mathur |
| author_sort | A. Voşki |
| collection | DOAJ |
| description | Abstract Reducing meat consumption, especially in high-intake countries such as the United States, is crucial in mitigating the climate and biodiversity crises and improving public health and animal welfare. Choice-architecture interventions or nudges in the food domain, such as choice defaults (e.g., reduced default portion sizes), can be powerful levers of behavior change. However, evidence remains limited in large-scale, real-life settings, and little is known about potential effects on diner satisfaction and backfiring effects that reduce or even reverse the desired behavior. These uncertainties have posed substantial barriers to scalability and wider adoption by the food service industry. In our single-blinded, quasi-experimental, pre-registered field interventions in Stanford University dining halls with staff-served portions, a 25% reduction in the serving spoon size (Study 1, 24 days, 364 diners, made-to-order burritos) produced a non-significant trend of 18% less meat served per day without reducing overall diner satisfaction (p = 0.059, d = 0.64) but with a wide CI that included the null (- 49.2, 1.07). A more substantial 50% reduction in serving spoon size (Study 2, 29 days, 1802 diners, varying menu items) did not reduce the amount of meat served (p = 0.60, d = 0.20), triggered backfiring effects, and significantly decreased diner satisfaction. Combining the two studies, the intervention did not significantly reduce meat consumption. While the trends in our findings are consistent with the ‘norm range model’—i.e., that moderate portion reductions may decrease intake but drastic reductions may prompt compensatory eating—key differences and contextual nuances between the two studies help explain the mixed results. Future studies on the ‘norm range’ of default portion size nudges to reduce meat consumption across different menu items and food service models is suggested to increase our understanding of effective and scalable interventions that facilitate collective shifts towards more sustainable dietary behaviors. |
| format | Article |
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| institution | OA Journals |
| issn | 1471-2458 |
| language | English |
| publishDate | 2025-04-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Public Health |
| spelling | doaj-art-ebbb54b7f25644dfb336c44903a9506c2025-08-20T02:27:13ZengBMCBMC Public Health1471-24582025-04-0125111510.1186/s12889-025-22495-9Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining hallsA. Voşki0M. Braginsky1A. Zhang2J. Bertoldo3S. Egan4L. A. Levig5M. Mueller Ihrig6M. B. Mathur7Emmett Interdisciplinary Program in Environment and Resources (E-IPER), Stanford Doerr School of Sustainability, Stanford UniversityDepartment of Psychology, Stanford UniversityQuantitative Sciences Unit, School of Medicine, Stanford UniversityStanford Dining, Hospitality and Auxiliaries, Residential and Dining Enterprises, Stanford UniversityStanford Dining, Hospitality and Auxiliaries, Residential and Dining Enterprises, Stanford UniversityStanford Dining, Hospitality and Auxiliaries, Residential and Dining Enterprises, Stanford UniversityStanford Dining, Hospitality and Auxiliaries, Residential and Dining Enterprises, Stanford UniversityQuantitative Sciences Unit, School of Medicine, Stanford UniversityAbstract Reducing meat consumption, especially in high-intake countries such as the United States, is crucial in mitigating the climate and biodiversity crises and improving public health and animal welfare. Choice-architecture interventions or nudges in the food domain, such as choice defaults (e.g., reduced default portion sizes), can be powerful levers of behavior change. However, evidence remains limited in large-scale, real-life settings, and little is known about potential effects on diner satisfaction and backfiring effects that reduce or even reverse the desired behavior. These uncertainties have posed substantial barriers to scalability and wider adoption by the food service industry. In our single-blinded, quasi-experimental, pre-registered field interventions in Stanford University dining halls with staff-served portions, a 25% reduction in the serving spoon size (Study 1, 24 days, 364 diners, made-to-order burritos) produced a non-significant trend of 18% less meat served per day without reducing overall diner satisfaction (p = 0.059, d = 0.64) but with a wide CI that included the null (- 49.2, 1.07). A more substantial 50% reduction in serving spoon size (Study 2, 29 days, 1802 diners, varying menu items) did not reduce the amount of meat served (p = 0.60, d = 0.20), triggered backfiring effects, and significantly decreased diner satisfaction. Combining the two studies, the intervention did not significantly reduce meat consumption. While the trends in our findings are consistent with the ‘norm range model’—i.e., that moderate portion reductions may decrease intake but drastic reductions may prompt compensatory eating—key differences and contextual nuances between the two studies help explain the mixed results. Future studies on the ‘norm range’ of default portion size nudges to reduce meat consumption across different menu items and food service models is suggested to increase our understanding of effective and scalable interventions that facilitate collective shifts towards more sustainable dietary behaviors.https://doi.org/10.1186/s12889-025-22495-9Default nudge Choice-architectureBehavior interventionPortion sizeMeat consumption |
| spellingShingle | A. Voşki M. Braginsky A. Zhang J. Bertoldo S. Egan L. A. Levig M. Mueller Ihrig M. B. Mathur Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining halls BMC Public Health Default nudge Choice-architecture Behavior intervention Portion size Meat consumption |
| title | Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining halls |
| title_full | Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining halls |
| title_fullStr | Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining halls |
| title_full_unstemmed | Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining halls |
| title_short | Effect of a portion-size default nudge on meat consumption and diner satisfaction: controlled experiments in Stanford University dining halls |
| title_sort | effect of a portion size default nudge on meat consumption and diner satisfaction controlled experiments in stanford university dining halls |
| topic | Default nudge Choice-architecture Behavior intervention Portion size Meat consumption |
| url | https://doi.org/10.1186/s12889-025-22495-9 |
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