Data_Sheet_1_Plant-based default nudges effectively increase the sustainability of catered meals on college campuses: Three randomized controlled trials.docx

BackgroundLiterature suggests limiting consumption of animal products is key to reducing emissions and adverse planetary impacts. However, influencing dietary behavior to achieve planetary health targets remains a formidable problem.
ObjectiveWe investigated the effect of changing the default meal option at catered events–from meat to plant-based–on participants' meal choices using three parallel-group, balanced, randomized controlled trials (RCT), and use these experimental results to project differences in plant-based default vs. meat default events on greenhouse gas emissions (GHGEs) (kg CO2 − eq), land use (m2), nitrogen (g N), and phosphorus (g P) footprint.
MethodsData collection was performed at three catered events (n = 280) across two college campuses. The selected experimental sites used convenience sampling. Events consisted of a graduate orientation, sorority dinner, and academic conference. Eligibility of individual participants included being 18 years or older and an invitation to RSVP for an enrolled event. Participants were randomly assigned to one of two groups: the control group received a RSVP form that presented a meat meal as the default catering option; whereas the intervention group received a form that presented a plant-based meal as the default. The primary outcome of interest in each group was the proportion of participants who selected plant-based meals. To explore environmental impacts, we modeled the footprints of four hypothetical meals. Using these meals and RCT results, the impact (GHGE, land use, nitrogen, phosphorus) of two hypothetical 100-person events was calculated and compared.
ResultsIn all, participants assigned to the plant-based default were 3.52 (95% CI: [2.44, 5.09]) times more likely to select plant-based meals than those assigned to the meat default. Using these results, a comparison of hypothetical events serving modeled meat-based and plant-based meals showed a reduction of up to 42.3% in GHGEs as well as similar reductions in land use (41.8%), nitrogen (38.9%), and phosphorus (42.7%).
ConclusionResults demonstrated plant-based default menu options are effective, providing a low-effort, high-impact way to decrease consumption of animal products in catered events. These interventions can reduce planetary impact while maintaining participant choice.

研究背景 已有研究文献表明，限制动物源食品消费是降低温室气体排放与减缓全球环境负面影响的关键举措。然而，通过引导饮食行为以实现全球健康目标仍是一项极具挑战性的难题。
研究目标 本研究依托三项平行组、均衡设计的随机对照试验（Randomized Controlled Trials, RCT），探究餐饮活动中默认餐食选项从肉类替换为植物基（plant-based）餐食对参与者餐食选择的影响；并基于上述实验结果，对比分析默认提供植物基餐食与默认提供肉类餐食的活动在温室气体排放（Greenhouse Gas Emissions, GHGEs，单位：kg CO₂当量）、土地占用（单位：m²）、氮素（单位：g N）及磷素（单位：g P）足迹方面的差异。
研究方法 本研究在两座大学校园的三场餐饮活动中完成数据采集，共纳入280名参与者，实验站点采用便利抽样法选取。三场活动分别为研究生迎新会、女生联谊会晚宴及学术会议。个体参与者的纳入标准为年满18周岁且受邀进行回复确认（RSVP）。参与者被随机分配至两组：对照组的回复表单将肉类餐食设为默认餐饮选项；干预组的回复表单则将植物基餐食设为默认选项。本研究的主要观测指标为两组中选择植物基餐食的参与者占比。为探究环境影响，我们构建了四种假设餐食的足迹模型；结合上述餐食模型与随机对照试验结果，计算并对比了两场假设的100人规模活动的环境影响（温室气体排放、土地占用、氮素及磷素足迹）。
研究结果 总体而言，被分配至植物基默认餐食组的参与者选择植物基餐食的概率是肉类默认餐食组的3.52倍（95%置信区间：[2.44, 5.09]）。基于上述结果，对比假设的肉类餐食与植物基餐食供应活动可知，前者的温室气体排放可降低最高达42.3%，土地占用、氮素足迹及磷素足迹也分别出现类似幅度的下降，分别为41.8%、38.9%及42.7%。
研究结论 本研究结果表明，设置植物基餐食为默认菜单选项可有效提升植物基餐食的选择率，为降低餐饮活动中动物源食品消费提供了一种低投入、高收益的干预手段。此类干预措施在保障参与者选择权的同时，可有效减缓全球环境影响。