The nature of the modern theory of healthy eating has been revealed in the article and the main areas of healthy eating have been determined. The aim is to study the theoretical components of the theory of a healthy diet. Conventional methods of analysis, synthesis, and generalization of the classical theory of nutrition have been applied and also healthy eating formation theory, which is formed under the auspices of the World Health Organization. Based on the theoretical and analytical studies, periods of evolution food have been scientifically justified: hunting and gathering, Neolithic revolution, of Discovery (XV-XVI centuries.) Great Industrial Revolution (XVII century.), The introduction of new technology (the twentieth century) classical theory of a balanced diet and its main provisions; the emergence of new types of different products. Attention is payed to the fundamental changes in lifestyle and diet structure of the XXI century. According to the results of the study it has been revealed that today there are such tendencies of improving nutrition: development of «exotic» cuisine of different nations, which is admired by a man-gourmet that overcomes many kilometers to taste a dish that is unusual for the area where a person resides; branching of «indirect» type of food. The basis of human life is to provide the necessary energy from food consumption, covering energy costs. Migration processes contribute to the formation of scientific theory approaches to a healthy diet. The human body gets to a not adapted food traditions and there is need for rationalization of food. The theory of nutrition requires to adhere to a number of established principles: calorie diet should meet energy costs, the chemical composition of food rations should meet the physiological characteristics and needs of the body for nutrients, guaranteeing balanced diet. Further research will focus on: research relationship between the individual micronutrients in the diet, including synergistic and antagonistic relationships; formation theory of healthy eating organic and inorganic products for children, students and adults; chemical composition of the agricultural products produced through the use of innovative production technologies.