Carbohydrates and fats are essential nutrients used to provide energy to the body. Carbohydrates provide energy quickly, while fats are a longer-lasting energy source. Fats are one of the building blocks of cell membranes and are necessary for the proper functioning of cells. They also enable the absorption of some vitamins (such as A, D, E, K). Carbohydrates, on the other hand, play a role in the energy production of cells and ensure the proper functioning of the nervous system. Fats provide thermal insulation by protecting the body from external temperature changes. This helps the body maintain its normal temperature. Some organs in the body, especially internal organs such as the heart, kidneys and liver, are protected by fat stores. The fatty tissue around these organs provides protection from impacts and injuries. Fats take part in the transport of fat-soluble vitamins (such as A, D, E, K) and ensure that these vitamins are in a usable form in the body. Carbohydrates and fats are an important part of a healthy nutrition program when consumed in a balanced manner and in appropriate amounts. However, when consumed excessively, they can cause health problems such as obesity. Therefore, it is important to pay attention to the consumption of carbohydrates and fats along with other nutrients in a balanced nutrition program. Some variants in genes involved in carbohydrate and fat metabolism affect individuals' response to carbohydrates and fat. Individuals can program their fat and carbohydrate intake in their diet according to their genetic predisposition.