Many Indigenous communities around the world have been experiencing rapid and profound diet changes. This case report uses a Sustainability Science lens to understand the characteristics of diet change in Indigenous Gunas communities of Panama, as well as its drivers and sustainability impacts. We use primary information collected through interviews with 30 experts and 232 household surveys in three Gunas islands characterised by different levels of development, western influence, and cultural erosion. We observe a rapid westernization of diets that has been mainly driven by closer interaction with tourists and the Panamanian society, as well as broader development processes. However, this diet change has a series of intersecting sustainability impacts related to food security, health, and socio-cultural and environmental change. It is necessary to understand the intersection of these phenomena when designing programs and interventions that seek to prevent or mitigate negative diet changes in Gunayala, and other Indigenous contexts more broadly.SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11625-023-01325-0.