Nutritional science is an interdisciplinary field that studies the nutrients necessary for the human body to survive, grow, develop, and carry out metabolic functions. Within this framework, nutrients are generally classified as macronutrients and micronutrients. Macronutrients refer to the nutrients that the body needs in high amounts for energy production and structural requirements. Carbohydrates, lipids (fats), and proteins make up the macronutrient group. These three basic nutrient groups have different but complementary functions in carrying out metabolic processes.

The fundamental approach in nutritional science is that macronutrients should be consumed not in isolation, but in a balanced and holistic distribution. While carbohydrates generally account for the largest share of daily energy needs, lipids and proteins not only provide energy but must also be consumed in the necessary proportions for maintaining cellular functions, hormone and enzyme synthesis, tissue repair, and the functioning of the immune system. This macronutrient balance varies depending on numerous factors such as an individual's age, gender, level of physical activity, current health status, metabolic characteristics, and lifestyle. For example, athletes and growing children require different macronutrient distributions due to their increased energy and protein needs, while in older individuals, protein intake plays a more critical role in maintaining muscle mass.