Voşki A, Braginsky M, Zhang A, Bertoldo J, Egan S, Levig L A, Mueller Ihrig M, Mathur M B
Emmett Interdisciplinary Program in Environment and Resources (E-IPER), Stanford Doerr School of Sustainability, Stanford University, 473 Via Ortega, Y2E2 Building, Suite 227, Stanford, CA, 94305, USA.
Department of Psychology, Stanford University, Stanford, USA.
BMC Public Health. 2025 Apr 16;25(1):1434. doi: 10.1186/s12889-025-22495-9.
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.
减少肉类消费，尤其是在美国等高摄入量国家，对于缓解气候和生物多样性危机、改善公众健康和动物福利至关重要。食品领域的选择架构干预措施或助推手段，如选择默认设置（例如，减少默认份量），可以成为行为改变的有力杠杆。然而，在大规模的现实生活场景中，相关证据仍然有限，而且对于对用餐者满意度的潜在影响以及减少甚至逆转期望行为的适得其反的效果知之甚少。这些不确定性对食品服务业的可扩展性和更广泛采用构成了重大障碍。在我们在斯坦福大学食堂进行的单盲、准实验、预先注册的现场干预中，服务人员提供的份量中，服务勺尺寸减少25%（研究1，24天，364名用餐者，定制墨西哥卷饼），每天提供的肉类减少了18%，但没有降低用餐者的总体满意度（p = 0.059，d = 0.64），但置信区间较宽，包含零值（-49.2，1.07）。服务勺尺寸更大幅减少50%（研究2，29天，1802名用餐者，不同的菜单项目）并没有减少提供的肉类量（p = 0.60，d = 0.20），引发了适得其反的效果，并显著降低了用餐者满意度。综合两项研究，该干预措施并没有显著减少肉类消费。虽然我们研究结果的趋势与“规范范围模型”一致，即适度减少份量可能会减少摄入量，但大幅减少可能会促使补偿性进食，但两项研究之间的关键差异和背景细微差别有助于解释这些混合结果。建议未来针对不同菜单项目和食品服务模式，研究默认份量助推以减少肉类消费的“规范范围”，以增进我们对促进集体转向更可持续饮食行为的有效且可扩展干预措施的理解。
