Transitioning to healthy and sustainable diets has high environmental and affordability trade-offs for developing countries

While dietary transitions offer benefits for both people and the environment globally, uncertainties persist regarding their impacts on the environment, human health, and food affordability across countries and over time. Here, we project water use, dietary quality, and food affordability from 2020–2100 under four healthy dietary scenarios and a baseline to assess potential challenges and opportunities at the country level over time. Using the MAgPIE model, we show that transitioning to healthy and sustainable diets could yield substantial enhancements in global dietary quality. However, in the initial phases, these transitions entail addressing water use and food affordability challenges. Yet, the advantages of transitions will manifest as the population and economy expand. By 2100, average dietary quality and food affordability could improve by 38.48% and 39.95%, and reduce water use by 10.82% globally. Nevertheless, we emphasize that sustainable development will be impeded in developing countries due to increased food demand, with a maximum deterioration in water use and food affordability of 2.54% and 29.25%, respectively. Although negative impacts will gradually subside as the dietary transition is completed, targeted interventions are still needed to improve water management and mitigate potential economic burdens during the dietary transition.