Mixtures of glycerol esters of a number of fatty acids, either saturated or unsaturated; fats and oils are insoluble in and immiscible with water.
Fats are nutrients found in animal products and plant foods such as nuts, whole-grain cereals, seeds, avocados, and olives. Nutrition experts generally recommend that fats should constitute no more than 30 percent of an individual’s total intake of calories each day. In addition, no more than 10 percent of daily calories should come from saturated fat. To lower the risk of heart disease and other health problems, doctors recommend that individuals reduce their total fat intake and replace some saturated fats with unsaturated fats. For individuals with atherosclerosis (arterial blockage from fat deposits), a diet even lower in fat content may be recommended.
Nutrients that supply the body with its highest density of energy are fats. They belong to the most extensive group of lipids and are composed of carbon and hydrogen atom chains, with only a small amount of oxygen. On a chemical level, they are predominantly made up of fatty acids that are bonded with glycerol. Typically, fats maintain a solid state at room temperature, whereas oils remain liquid.
Fats and oils can be categorized into two main types – saturated and unsaturated – based on the number of hydrogen atoms they hold. Saturated fats are those in which the fatty acids carry the highest possible amount of hydrogen. Conversely, unsaturated fats are those where some carbon chain locations aren’t filled by hydrogen. If only a single site could accommodate an additional hydrogen atom, these fats are termed monounsaturated. However, if there are multiple unfilled sites, the fats are identified as polyunsaturated. Animal fats, which are mostly found in meat and dairy products, are predominantly saturated, while vegetable fats are generally unsaturated.
The quantity and kinds of fat consumed in a diet significantly impact health. Consuming a diet high in fats, especially saturated fats, has been associated with obesity and a heightened risk of atherosclerosis, which involves fat depositing on artery walls and can lead to coronary artery disease and stroke. Other severe health conditions tied to excessive fat intake include breast, colon, and prostate cancers, along with type 2 diabetes mellitus.
Some types of dietary fats, particularly triglycerides, which are compounds of glycerol and three fatty acids, are responsible for providing fat-soluble vitamins A, D, E, and K, in addition to essential fatty acids.
Triglycerides represent the primary form of fat storage in the body. These reserves serve as an energy source and also offer insulation and protection for vulnerable organs like the heart and kidneys. Phospholipids, another type of fats, form an integral part of cell membranes. Sterols, such as cholesterol, present in both animal and plant tissues, fulfill various roles and are crucial for the production of hormones and vitamins. Both phospholipids and sterols are synthesized in the body using the nutrients obtained from the diet.
Before being metabolized by lipase, a pancreatic enzyme, dietary fats are first broken down into microscopic particles in a process called emulsification, facilitated by bile salts. After this process, they are absorbed through the lymphatic system prior to entering the bloodstream.
In order to be transported in the blood, lipids bind with proteins, at which point they become known as lipoproteins. There are four primary classes of lipoprotein: chylomicrons, high-density lipoproteins (HDLs), low-density lipoproteins (LDLs), and very low-density lipoproteins (VLDLs). LDLs and VLDLs, sometimes referred to as ‘bad fats’, carry substantial amounts of cholesterol, which they distribute throughout the bloodstream and deposit in tissues. On the other hand, HDLs, often termed ‘good fats’, collect cholesterol and return it to the liver for processing and removal. High concentrations of LDLs are linked with atherosclerosis, whereas HDLs provide a protective effect.