Iran's simple and environmentally extended commodity by commodity input-output (IO) model was used to determine the impacts of dietary changes on the Iranian economy and on the environmental load. The original model is based on the status-quo diet and was modified to include the World Health Organization (WHO), the World Cancer Research Fund (WCRF) and Mediterranean alternative dietary scenarios. A range of impacts occurred depending upon the relative changes in food items. The direction of changes was similar in the three alternative scenarios. The greatest and smallest impact occurred in the WHO and the Mediterranean scenarios respectively. Total changes in output in WHO, WCRF and Mediterranean dietary scenarios were calculated to be 7010.1, 4802.8 and 3330.8 billion Rials respectively. The outputs of rice, vegetables, fruit, bread and macaroni decreased, but those of live and other animal products increased. The output of non-food commodities and services increased as well. The environmental load increased for three dietary scenarios in comparison with the status-quo diet. The greatest and smallest environmental load occurred in WHO and Mediterranean dietary scenarios respectively. Thus, although dietary changes can have positive effects on economic output, in order to avoid negative environmental effects, it is necessary to consider strategies such as applying capabilities, particularly natural resources in an optimal healthy and environmentally diet, planning for improving forest covering and green space simultaneously with increasing economic activities and using indirect incentives, such as taxes and insurance, for promoting sustainable and healthy foods and reducing greenhouse gas emissions.