How may we effectively motivate people to reduce the consumption of meat? Results of a meta-analysis of randomized clinical trials

Purpose Excessive meat consumption (MC) is associated with multiple health risks. Additionally, it can undermine environmental sustainability and affect the potential improvement of animal welfare. The aim of this study was to assess the efficacy of literacy interventions (LIs) in reducing MC. Methods Studies assessing the efficacy of LIs addressing health risks, environmental sustainability and/or animal welfare in reducing MC were searched. We used random-effects meta-analysis to estimate the overall efficacy and conducted subgroup analyses to identify the most effective information contents. Additionally, meta-regression analyses investigated participants' age, LI duration, and follow-up length influence on LIs' efficacy. Results Fourteen studies involving more than ten thousand subjects were meta-analyzed. The pooled estimate showed that LIs had a small (Hedges's g = 0.15; 95%CI: 0.06–0.25) but statistically significant effect in reducing MC. Subgroup analysis showed that the highest efficacy was achieved when subjects were alarmed about health risks (g = 0.29; 95% CI: −0.02, 0.60), when compared to informing about the risks for the environment (g = 0.18; 95% CI: −0.15, 0.51) and for animal welfare (g = 0.02; 95%CI: −0.08, 0.11). The meta-regression analysis indicated that LIs had greater efficacy in younger individuals and when the intervention duration was longer. Conversely, it was suggested that efficacy improves as the length of follow-up increases. Conclusions Informing about health risks related to MC temporarily decreased its intake, while informing about the impact on environmental sustainability or animal welfare was ineffective. Furthermore, long-lasting LIs achieve long-term dietary change toward MC.