Human diet is responsible for a number of environmental problems. It is a driving force for water and land requirements for food production. This contribution investigates the relationships between diet and agricultural production, the resulting mass flows of nitrogen and phosphorus, their impact on the aquatic environment, the agricultural area requirements and emissions of nitrogen to the atmosphere in a clearly defined region. The combination of material flow analysis, nutrient emission model and statistical input data determines the reference state. By changing some input data (changing diet) several independent processes change. Thus the impacts of changing nutrition patterns can be investigated for a well-defined region. According to diet recommendations a scenario was developed and impacts on resources and environment drawn. Application of the method to Austria shows a 30% reduction of agricultural land requirements for food production by changing nutritional habits to a healthy balanced diet. Nitrogen export via rivers would be decreased by 11%. The diet change would also result in a reduced fertilizer input by 6% to agriculture, which is relevant especially for the limited resource phosphorus.