The topic of the paper is the study of the diet problem of a student within the framework of sustainable development. The work is primarily intended for students, people who have the status of a student and the right to perform student work, for the reason that was necessary to calculate the food budget, which is based on the minimum student hourly wage, but the work can also be used by individuals who strive to reduce costs. After finding out the prices of the cheapest products in certain retail chains in Zagreb, data was obtained on how much each product contains certain nutrients and calories. Research methods included a compilation method that used data and models from other similar works and a modeling method that created a model of the problem that included various constraints and an objective function. The recommended minimum and maximum daily intakes of nutrients, as well as the minimum daily intake of calories, were used as model constraints. The goal of the work was to find an optimal combination of products that provides sufficient intake of nutritional values for achieving a healthy diet, and which minimizes food costs. A diet for three days was prepared, the first day consisted of three meals, the second of two (although four meals were planned) and the third of two meals. Total costs for the first day are €3.93, for the second €4.37, and for the third day €9.20. The lowest possible food budget amount of €700.8 and the highest possible total food cost of €166.7 were compared, which led to the conclusion that there is no case in which the budget amount is not sufficient to cover food costs. Later, the dual problems of the models for all three days are presented, as well as the sensitivity analysis.