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Description: Which interventions produce the largest and most enduring reductions in consumption of meat and animal products (MAP)? We address this question with a theoretical review and meta-analysis of randomized controlled trials that measured MAP consumption at least one day after intervention. We meta-analyze 35 papers comprising 41 studies, 112 interventions, and approximately 87,000 subjects. We find that these papers employ four major strategies to change behavior: choice architecture, persuasion, psychology, and a combination of persuasion and psychology. The pooled effect of all 112 interventions on MAP consumption is quite small (standardized mean difference (SMD) = 0.07 (95\% CI: [0.02, 0.12]), indicating an unsolved problem. Interventions aiming to reduce only consumption of red and processed meat were more effective: SMD = 0.25 (95\% CI: [0.11, 0.38]), but it remains unclear whether such interventions increase consumption of other forms of MAP. Incorporating a set of marginal studies that meet most but not all of our inclusion criteria inflates the pooled effect size to SMD = 0.2 (95\% CI: [0.09. 0.31]). We conclude that while no theoretical approach provides a proven remedy to MAP consumption, designs and measurement strategies have generally been improving over time, and many promising interventions await rigorous evaluation.