Fats are, alongside carbohydrates and proteins, a vital part of food. With an energy density of 9 kcal/g, they are the highest form of all energy sources and provide important storage of energy. They also provide important materials that the body cannot manufacture itself, such as essential fatty acids (e.g. linol and linolen acids) and fat-soluble vitamins (A, D, E, and K).

Fats are very important flavour carriers in food.

Dietary fats predominantly consist of triacylglycerides (TAGs) or short triglycerides. These are made from three fatty acids, which are compounds of the trivalent alcohol, glycerine.