Why understanding food choice is crucial to transform food systems for human and planetary health.

What, how and why people eat has long been understood to be important for human health, but until recently, has not been recognised as an essential facet of climate change and its effects on planetary health. The global climate change and diet-related health crises occurring are connected to food systems, food environments and consumer food choices. Calls to transform food systems for human and planetary health highlight the importance of understanding individual food choice. Understanding what, how and why people eat the way they do is crucial to successful food systems transformations that achieve both human and planetary health goals. Little is known about how food choice relates to climate. To clarify potential paths for action, we propose that individual food choice relates to climate change through three key mechanisms. First, the sum of individual food choices influences the supply and demand of foods produced and sold in the marketplace. Second, individual food decisions affect type and quantity of food waste at the retail and household level. Third, individual food choices serve as a symbolic expression of concern for human and planetary health, which can individually and collectively stimulate social movements and behaviour change. To meet the dietary needs of the 2050 global population projection of 10 billion, food systems must transform. Understanding what, how and why people eat the way they do, as well as the mechanisms by which these choices affect climate change, is essential for designing actions conducive to the protection of both human and planetary health.