Prospects of food taxes for planetary health: a systematic review of modeling studies

Background Fiscal policies on food can effectively fight the growing burden of non-communicable diseases and climate change. These policies should be modeled in advance to see the implications for the environment and health. The aim of this study was to analyze these modeling methodologies.Methods We conducted a systematic review, searching Scopus and Pubmed for studies that modeled fiscal policies on the food groups targeted by the EAT-Lancet Commission and examined their health or environmental outcomes. We then double-screened the records, and extracted data on modeling methods from the 55 included studies. The review protocol was registered on PROSPERO (2022 CRD42022291945).Results The most frequently modeled interventions were fruit and vegetable subsidies and carbon taxes on food. One study also included a consumer education campaign to enhance the effect of fiscal policy. The outcomes are highly sensitive to consumption change and price elasticities. The stability of the amount of diet consumed was modeled 6 times with calorie stability, and twice with dietary weight stability. The outcomes were also sensitive to diseases and the system boundaries of environmental impacts. None of the studies modeled the health effects of environmental outcomes.Conclusions We did not find a model that covered all the relevant aspects of the issue. Some parts were missing from all the included models. It is advisable to model the stability of the amount of diet consumed, either by keeping the weight of the diet stable or by taking a more conservative approach and keeping the consumed calories stable. A fiscal policy is more equitable if a tax and a subsidy are combined to be less regressive. Additionally, an informational campaign as a complement could improve effectiveness. The included diseases and environmental boundaries are preferable to be broad to have more valid outcomes on this complex issue. A more comprehensive understanding of fiscal policies would allow us to better anticipate the impact of our actions and inactions and thus could lead to more sophisticated measures taken by policymakers.