Function of Fats:
Along with proteins, fats constitute major components of body fluids and cell membranes. The two essential fatty acids (EFA) namely Linoleic (LA n-6) and Alpha-Linolenic (ALA n-3) acids are metabolized at various sites in the body to generate a group of biologically active compound, which perform several important functions.
1. Body Composition:
All body cells contain some fat. In healthy non-obese women fat makes up about 18-25% of body weight. In healthy non-obese men about 15-20% of body weight. With aging the proportion of fat in the body generally increases as that of active tissue decreases.
2. Insulation and Padding:
The subcutaneous layer of fat is an effective insulator that reduces losses of body heat in cold weather. Excessive layers of subcutaneous fat, as in obesity, interface with heat loss during warm weather, thereby increasing discomfort. Vital organs such as the kidney are protected against physical injury by a padding of fat.
3. Energy:
The primary function of fat is to supply energy. Each gram of fat when oxidized yields approx. 9 Kcal or more than twice as much energy as one gram of carbohydrate or protein. The high density and low solubility of fats make them an ideal form to store energy. In fact, not only fats are stored in adipose tissue but any glucose and amino acids not promptly utilized are also converted into fats and stored.
4. Satiety:
Closely related to the provision of energy is the satiety value of fats. Because fats reduce gastric motility and remain in the stomach longer, the onset of hunger sensation is delayed. Diets that contain generous amounts of fat are sometimes described as “rich” or “satisfying” that is they have satiety value.
5. Palatability:
How much food we eat as well as the kind of food we eat depend in part on our enjoyment of it. Fats lend palability to the diet, whether it be as butter or margarine on bread, seasoning for vegetables, dressing on stables or an ingredient of cakes, pastries and other desserts. The fats in meats, poultry and fish and the oils in fruits lend the characteristics flavors that we enjoy. If most fat eliminated from the diet, as it is necessary for patients with disturbances of fat metabolism, the diet becomes very bulky.
6. Carriers of Fat-Soluble Vitamins:
Dietary fat is a carrier of the fat soluble vitamins A, D, E and K. Some fat is also necessary for the absorption of vitamin A and its precursor, carotene.