Fat Metabolism and Nutrition Glossary

Disclaimer: The information in this glossary is introductory in nature and should not be interpreted as complete. Biochemistry and nutrition are highly complex areas of science. This glossary is ©2005-2006-2011 Microlipid Technologies, Inc., all worldwide rights reserved. This glossary may not be copied or reproduced for commercial use, or displayed online in any third party website, without prior written consent.

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Organic compound with carbon atoms joined together in straight or branched chains. Fatty acids are aliphatic compounds.

Molecules that slow or prevent undesirable chain reactions during oxidation. Oxidation, an essential life process, is like a forest fire that is difficult to stop. Normal oxidation creates destructive byproducts called free radicals. Living organisms have adapted a complex series of free radical “firefighters” called antioxidants, molecules that bind to free radicals before the latter are able to damage healthy cells. Examples of antioxidants include Vitamin C, Vitamin E, Selenium, Catalase enzyme and various phytochemicals found in whole grains.

Disease caused by the gradual buildup of fatty deposits in the arterial blood vessels. The coronary arteries become inflamed in response to lipoprotein deposits (plasma proteins that carry cholesterol and triglycerides) in the walls of arteries. As the deposits slowly narrow the arteries, the heart receives less blood. Diminished blood flow may eventually cause chest pain (angina), shortness of breath or other symptoms. A complete blockage can cause a heart attack. The more common term for Atherosclerosis is “hardening” of the arteries.


Manufacturing process whereby pigments, impurities, trace metals, gums and oxidized materials are removed from oils and fats by absorptive cleansing using bleaching clays or activated carbon. Bleaching of edible oils or fats is generally carried out under vacuum at 70–120°C.


Waxy substance that occurs naturally in the cell membranes of all body tissues and is transported in the blood plasma of all animals. Trace amounts of cholesterol are also found in plant membranes. The body needs cholesterol to produce hormones, vitamin D and bile acids that aid in fat digestion. Cholesterol is a sterol (combination of steroid and alcohol) lipid. The term is derived from the Greek words chole (bile) and stereos (solid), and -ol, the chemical suffix for alcohols. Most cholesterol is synthesized by the body. Cholesterol is insoluble in blood and is transported through the circulatory system bound to lipoproteins. “Bad” cholesterol refers to cholesterol contained within LDL (low-density lipoprotein) which, according to the lipid hypothesis, is thought to have harmful actions. “Good” cholesterol refers to cholesterol contained within HDL (high-density lipoprotein), thought to have beneficial actions.

Cis configuration.
Fatty acid chain arranged with adjacent carbon atoms on the same side of a double bond. Double bonds are more rigid than single bonds, so cis configurations are less flexible in closely packed space. The rigidity of the double bonds combines with the unbalanced shape to curve the chain. For example, oleic acid, with one double bond, has a kink, while linoleic acid, with two double bonds, has a more pronounced bend. Alpha-linolenic acid, with three double bonds, usually has a hooked shape. The presence of cis bonds limits the density of fatty acids and can thus lower their melting temperatures.

Clearance rate.
Volume of biological fluid completely cleared of drug metabolites as measured in unit time. Elimination occurs as a result of metabolic processes in the kidney, liver, saliva, sweat, intestine, heart, brain, or other site.

Cold pressing.
Also called expeller pressing. A method of extracting oil by crushing seeds in a press. Cold pressing enhances stability and helps preserve the nutritional components of edible oils by avoiding the use of chemical solvents and high temperatures. Cold pressing thus produces higher quality oils than solvent extraction, a chemical process involving higher temperatures and solvents such as hexane.

A mixture in which one substance is dispersed evenly throughout another. A colloidal system consists of two separate phases: a dispersed phase (or internal phase) and a continuous phase (or dispersion medium). A colloidal system may be solid, liquid or gaseous. Milk is an emulsified colloid of liquid butterfat globules dispersed within a water-based liquid.

Condensation reaction.
Chemical reaction in which two molecules combine to form a single molecule, with the loss of a small molecule. A dehydration reaction occurs when the lost small molecule is water.


Desaturase enzyme.
An enzyme which removes two hydrogen atoms from an organic compound to create a carbon-carbon double bond.

Acronym for “Dietary Supplement Health and Education Act of 1994,” a U.S. law that requires dietary supplement manufacturers to ensure that dietary supplements are safe before being marketed and sold. The U.S. Food and Drug Administration (FDA) is responsible for taking action against any unsafe dietary supplement product after it reaches the market. Generally, manufacturers do not need to register their products with FDA or apply for FDA approval before producing or selling dietary supplements. Manufacturers are required to ensure that product label information is truthful and not misleading. Dietary supplement advertising is regulated separately by the U.S. Federal Trade Commission (FTC).


Essential fatty acids.
Polyunsaturated fatty acids that include the omega-3 and omega-6 fatty acids. The term “essential” refers to the fact that these fatty acids are required by the body but can only be obtained from food. Mammals can manufacture saturated and monounsaturated fatty acids with a double bond at the omega-9 position, but do not produce the enzymes necessary to generate a double bond at the omega-3 or omega-6 position. Two essential fatty acids, linoleic acid (LA) and linolenic acid (LNA), are found only in plant oils. Fish oils contain the longer-chain omega-3s, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Essential fatty acids are used to produce hormone-like substances that regulate a wide range of functions including blood pressure, blood clotting, blood lipid levels, immune and inflammation responses, brain activity and heart electrical function.

Chemical reaction in which two chemicals (typically an alcohol and an acid) form an ester. Esters often have a pleasant fruity odor and are the basis for many commercial fragrances and food flavorings.


Major dietary nutrient that serves as an energy source and vitamin transport mechanism. Fat and carbohydrate molecules are all built of the same three elements: carbon, hydrogen and oxygen. However, fats have more carbon and hydrogen and less oxygen and can supply more than twice the energy of the same weight in carbohydrates (nine calories per gram versus four). This fact, combined with the shape of certain types of fat molecules, makes fat the most efficient way to store energy in the body. Dietary fat also transports and aids absorption of the fat-soluble vitamins A, D, E and K.

Fatty acid.
Informal chemical name for fat. A fatty acid has a carboxylic acid at one end of a long unbranched aliphatic chain that can be either saturated (each carbon bonded to two hydrogen atoms) or unsaturated (at least one carbon bonded to only one hydrogen atom, with a double bond to a neighboring carbon atom), with a methyl group at the other end. Monounsaturated fatty acids have one double bond and polyunsaturated fatty acids have two or more double bonds. Saturated and unsaturated fatty acids differ in energy content and melting point. Since an unsaturated fat contains fewer carbon-hydrogen bonds than a saturated fat with the same number of carbon atoms, unsaturated fats will yield slightly less energy during metabolism than saturated fats with the same number of carbon atoms. Carbon atoms in a fatty acid are identified by Greek letters, based upon their relative distance from the carboxylic acid. The closest carbon atom is the alpha carbon, the next carbon is the beta carbon, and so on. In a long-chain fatty acid, the carbon atom in the methyl group is called the omega carbon because omega is the last letter of the Greek alphabet. All fatty acids are composed of alkyl groups or hydrocarbon chains containing from 4 to 22 carbon atoms. Natural fats and oils have an even number of carbon atoms, with at least eight, because the precursor molecule of fatty acid synthesis (acetyl-Coenzyme A) has a two-atom carbon group. Fatty acids are the building blocks of fats. Every human cell contains fatty acids.

Free radicals.
Molecules with unpaired electrons. The unpaired electrons make a free radical unstable, which can lead to undesirable chemical reactions as the free radical seeks to react with any molecule that can contribute the missing electron(s). Free radicals are normal byproducts of oxidation.

Functional foods.
Any fresh or processed food that may provide health benefits beyond basic nutrition. Functional foods are sometimes called nutraceuticals. Examples include cereals fortified with vitamins and minerals, tomatoes bred for increased levels of lycopene, milk fortified with acidophilus a probiotic bacterium.

Functional group.
Specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of such molecules. Each cluster of atoms of the same type of functional group will undergo the same chemical reactions regardless of the number of similar functional groups within a given molecule.


Also called dextrose. Sugar that is the body’s chief source of energy. Glucose is considered a simple sugar. Found in the blood, it is the main sugar the body manufactures. The body makes glucose from all three elements of food: protein, fat and carbohydrates, but in largest part from carbohydrates. Glucose serves as the major source of energy for living cells. It is carried to each cell through the bloodstream. Cells cannot use glucose without the help of insulin.

Acronym for “Generally Recognized as Safe,” a U.S. Food and Drug Administration (FDA) designation that a chemical or substance added to food is considered safe by experts. Under sections 201(s) and 409 of the Federal Food, Drug, and Cosmetic Act (the Act), any substance intentionally added to food is a food additive subject to premarket review and approval by the FDA, unless the substance is generally recognized, among competent scientists, as having been adequately shown to be safe under the conditions of its intended use, or unless the use of the substance is otherwise excluded from the definition of a food additive. Substances that meet the definition of a pesticide, a dietary ingredient of a dietary supplement, a color additive, a new animal drug or a substance approved for such use prior to September 6, 1958, are excluded. For food additives introduced after 1958, significant safety data or other information used to arrive at a GRAS determination must be made publicly available. The Act covers substances that might migrate into food from packaging, traditional food additives and even common food ingredients such as sugar and salt. GRAS exceptions exist so the FDA does not waste resources reviewing substances that clearly are safe.


More correctly called n-hexane, a chemical made from petroleum crude and mixed with a variety of solvents for different uses. n-Hexane is used to extract vegetable oils from crops such as soybeans. Several consumer products contain n-hexane, including gasoline, quick-drying glues and rubber cements. n-Hexane is used as a cleaning agent in the printing, textile, furniture and shoemaking industries, and is an ingredient in special glues used by the roofing, shoe and leather industries. The chemical evaporates very easily into the air, where it is broken down within a few days. n-Hexane spilled into water will float to the surface and evaporate. n-Hexane spilled on the ground will typically evaporate before it can soak into the soil. n-Hexane is not harmful in small amounts and does not concentrate in animals, fish or plants. (Anyone who pumps gas breathes tiny amounts of n-hexane.) However, inhaling high amounts of n-hexane can cause nerve damage and paralysis of the limbs (the first symptom is numbness in the hands and feet). Enclosed work areas with high concentrations of n-hexane (generally greater than 500 ppm) should be well ventilated.

Manufacturing process that adds hydrogen gas and a metal catalyst to a batch of edible oil under high temperature (typically 248 to 410 degrees Fahrenheit) and pressure. Partial hydrogenation makes an oil more dense; complete hydrogenation turns a liquid oil into a solid, or saturated, fat. Hydrogenation increases product shelf life and allows inexpensive cooking oils to simulate more expensive food ingredients like butter and animal fat. Margarine and shortening are hydrogenated oil products. Hydrogenated oils are traditionally used in ice cream, cookies, potato chips and other snack foods, french fries, onion rings, chocolate products and various other baked goods. Partially hydrogenated oil is often used as a substitute for butter because is it less expensive and has a longer shelf life, but still has butter’s creamy texture and flavor-enhancing properties. However, the low cost, extended shelf life and flavor stability of hydrogenation come with a cost: When an oil is only partially hydrogenated, a certain percentage of the fat molecules are changed into trans fats.

Chemical reaction or process in which a chemical compound reacts with water. Hydrolysis is the opposite of a condensation reaction, during which two molecular fragments are joined for each water molecule produced.

Physical property of a charge-polarized molecule that can bond with water through hydrogen bonding. Hydrophilic molecules are typically soluble not only in water but also in other polar solvents. They dissolve more readily in water than in oil or other hydrophobic solvents. Hydrophilic molecules consist of alcohol and fatty acyl chains. Some hydrophilic substances (e.g. colloids) do not dissolve.

Physical property of a non-polar molecule that is repelled from water. Hydrophobic molecules in water often cluster together, forming micelles. Water is electrically polarized and is able to form hydrogen bonds internally. Hydrophobic molecules are not electrically polarized and—because they are unable to form hydrogen bonds—water repels hydrophobes in favor of bonding with itself.


Not capable of being dissolved. Fats are insoluble in water because fat is non-polar and water is polar. Fats are soluble in non-polar solvents such as acetone and ether.


Acetone, acetoacetate and beta-hydroxybutyrate are ketones (also called ketone bodies) generated from carbohydrates, fatty acids and amino acids in humans and most vertebrates. Ketones are elevated in blood after fasting including a night of sleep, and in both blood and urine in starvation, hypoglycemia due to causes other than hyperinsulinism, various inborn errors of metabolism, and ketoacidosis (usually due to diabetes mellitus). Although ketoacidosis is characteristic of decompensated or untreated type 1 diabetes, ketosis or even ketoacidosis can occur in type 2 diabetes in some circumstances as well. Acetoacetate and beta-hydroxybutyrate are an important fuel for many tissues, especially during fasting and starvation.

The brain relies heavily on ketone bodies as a substrate for lipid synthesis, to produce energy during periods of reduced food intake. Ketones have been described as “magic” in their ability to increase metabolic efficiency, while decreasing production of free radicals, the damaging byproducts of normal metabolism. Ketone bodies may be therapeutic for neurological diseases such as Alzheimer’s and Parkinson’s, and research suggests the heart and brain operate about 25 percent more efficiently with ketone bodies than with glycogen, the body’s regular fuel. When drug therapy is unsuccessful in reducing epileptic seizures, a Ketogenic Diet that is very high in fat, with near-zero carbohydrate intake, can be effective in reducing seizures for some patients (especially children).

Metabolic process that occurs when the body converts fatty acids into ketone bodies, water-soluble compounds that can be used for energy. Glucose is the body’s primary energy source. The usual sources of glucose are dietary carbohydrates. However, the body is designed to burn fat when dietary carbohydrates are not available, and to send certain types of fatty acids—medium chain fatty acids (MCTs)—to the liver where they are immediately converted into ketone bodies through lipolysis. This immediate transport and metabolism of MCTs is sometimes called the ketogenic pathway.


Generic name for a group of enzymes that catalyze the hydrolysis of lipids.

Lipid peroxidation.
A chain reaction process involving oxidative degradation of lipids. Free radicals steal electrons from the lipids in cell membranes, resulting in cell damage. Polyunsaturated fatty acids are the most susceptible to lipid peroxidation because of their more reactive chemical structures.

Compounds of fatty acids and glycerol. Lipids are the most efficient energy source for living things. They are stored beneath the skin in animals and in the seeds of plants. Food lipids include animal fats, which are solid at room temperature, and vegetable oils, which are liquid at room temperature. Cholesterol is a sterol compound manufactured by animals to produce certain steroid hormones. Cholesterol is not found in plants.

Breakdown of stored fat for use as energy. Lipolysis occurs primarily in the liver and releases free fatty acids into the lymph system and then into the bloodstream. Triacylglycerol molecules are split into three fatty acid chains and one glycerol molecule (hydrolysis by lipases). Once released into the blood, fatty acids are transported to tissues that require energy.


MCT oil.
See medium-chain triglycerides. MCT oil is typically distilled by steam from coconut oil and has been used since the 1950s to provide nutrition to hospital patients suffering from malabsorption. While coconut oil contains up to 62 percent MCT content, premium grade MCT oil is typically comprised of the first fractional distillate of coconut oil, which includes the fatty acids C6 (caproic acid), C8 (capryllic acid) and C10 (capric acid), together totalling about 15 percent of coconut oil content. More recently, MCT oil has been used as a nutrition supplement by bodybuilders seeking a dense calorie food source that will not add to body fat. MCT oil is also available as a distillate of oil palm.

Medium-chain triglycerides (MCTs).
Fatty acids with six to 12 carbon atoms. These fatty acids are constituents of coconut and palm kernel oils and are also found in camphor tree drupes. Coconut and palm kernel oils are also called lauric oils because of their high content of the 12-carbon fatty acid, lauric or dodecanoic acid. Coconut oil contains up to 62 percent medium-chain fatty acids. Butter contains about 12 to 15 percent short- and medium-chain fatty acids. This type of saturated fat does not need to be emulsified by bile salts and is absorbed directly from the small intestine into the liver, where it is converted into quick energy. MCTs also have antimicrobial, antitumor and immune system support properties. Unlike most oils of animal or vegetable origin, the natural saturation of the medium-chain fatty acids makes them stable and resistant to oxidation. In other words, they deliver long shelf life without the need for commercial hydrogenation.

Metabolic pathway.
A series of chemical reactions that occur within a living cell. In each pathway a principal chemical is modified by chemical reactions. These reactions are catalyzed by enzymes. Dietary minerals, vitamins and other cofactors are often required by the enzyme to perform the chemical reaction.

An aggregate of surfactant molecules dispersed in a liquid colloid. A micelle in aqueous solution usually forms an aggregate with hydrophilic “head” regions in contact with a surrounding solvent, sequestering the molecules’ hydrophobic tails in the micelle center. The size and typically spherical shape of micelles are a function of the molecular geometry of the surfactant molecules and solution conditions such as surfactant concentration, temperature and pH.

Miscibility refers to the property of different liquids to mix and form a homogeneous solution.

Small molecule that may become chemically bonded to other monomers to form a polymer. Plastics are created when hydrocarbon monomers such as phenylethene and ethene form polyphenylethene (polystyrene) and polyethene (polyethylene). Amino acids are natural monomers that polymerize to form proteins. Glucose monomers can also polymerize to form starches, amylopectins and glycogen polymers. The term is derived from the Greek words mono (one) and meros (part).

Monounsaturated fatty acids.
Fatty acids containing one double bond. Examples of foods high in monounsaturated fat include avocados, nuts, and canola, olive and peanut oils. Research suggests that increased consumption of monounsaturated fats (for example eating more nuts) is beneficial in lowering LDL (“bad”) cholesterol and lowering the risk of coronary heart disease.


Novel foods.
Foods considered new for human consumption. Novel foods must obtain government approval before introduction into the public food supply. A food or food ingredient is considered novel if it possesses a new or intentionally modified molecular structure (e.g. synthetic fat substitutes or fillers), it comes from a plant unknown in Europe (e.g. new, exotic fruits, herbs, or spices), it consists of microorganisms, fungi, or algae that are new to the human diet, or it is produced using novel technologies (e.g. new conservation or purification techniques). Novel foods are governed by the European Union’s novel food directive (258/97). Until the end of 2003, genetically modified organisms were regulated according to the novel food directive. Today, genetically modified foods are governed by a separate directive (1829/2003).


Brand name for Olestra, a sucrose polyester fat substitute developed by Procter & Gamble. See Olestra.

Sucrose polyester developed by Procter & Gamble and approved by the FDA as a fat substitute, but only for use in snack foods. Olestra has a sucrose backbone with up to eight fatty acid chains arranged radially like an octopus. The polymer is too large to move through the intestinal wall, and because the molecule does not contain glycerol, the digestive process cannot remove the fatty acid tails from the sucrose molecule. As a result, Olestra passes through the digestive system intact, adding no calories or nutritional value to the diet. Olestra is made by combining soybean or cottonseed oil with ordinary sugar through an esterification process. Also known as Olean®, Procter & Gamble’s brand name for the polymer. Olestra was first synthesized by P&G chemists in 1968 but did not obtain FDA approval until 1996. Olestra has the same taste and mouth feel as fat.

Chemical reaction that transfers electrons from a substance to an oxidizing agent.


Nutrition delivery into a vein, bypassing the digestive system. Parenteral feeding is sometimes also called intravenous feeding and may be used for patients who cannot absorb nutrients through the intestinal tract because of intestinal disease, vomiting, severe diarrhea, or the prospect of the latter two conditions, as in patients undergoing chemotherapy, radiation or bone marrow transplantation. Parenteral nutrition can provide 100 percent of nutrition requirements.

Substance composed of molecules having large molecular mass, with repeating structural units (monomers) connected by covalent chemical bonds. The term is derived from the Greek words polys (many) and meros (parts). The individual molecules which comprise a polymer are referred to as polymer molecules, where the word polymer functions as an adjective. DNA and plastics are two common polymers.

Polyunsaturated fatty acids.
Fatty acid molecules with more than one double bond, in other words, with two or more points capable of supporting but missing hydrogen atoms. The lack of hydrogen atoms reduces the molecule’s intermolecular forces, which lowers its melting point.


Condition in which an off-flavor has developed in an edible oil or fat, or manufactured food product, caused by oxidative deterioration. Primary oxidation products are odorless and tasteless but certain secondary decomposition products have particularly potent off-flavors and are detected by the palate at extremely low concentrations. The term rancidity is sometimes also used to describe the soapy taste resulting from the hydrolysis of lauric oils, which is due to the short chain fatty acids formed.

Acronym for “Refined, Bleached and Deodorized.” Bleaching and deodorization are processing steps for refined cooking oils, which may be referred to in commodity vegetable oil price quotes by the prefix RBD.


Feeling of satisfaction or “fullness” following the consumption of food that quells the desire for additional food. Satiety is related to appetite regulation, hunger and the control of food intake.

Saturated fatty acids.
Fatty acids without double bonds or other functional groups along the chain. Saturated means that all the carbons (except the carboxylic acid group) contain as many hydrogens as possible. Saturated fatty acids form straight chains and so can be packed together very tightly, allowing very dense chemical energy storage for living organisms. The fatty tissues of animals contain significant amounts of long-chain saturated fatty acids.


Trans configuration.
Fatty acid chain arranged with adjacent carbon atoms on opposite sides of a double bond. As a result, the fatty acid chain tends not to bend much, and the shape is similar to straight saturated fatty acid chains. A molecule in trans configuration has a higher melting point than the same molecule in cis configuration. Most fatty acids in the trans configuration (trans fats) are not found in nature and are the result of industrial hydrogenation.

Trans fat.
Trans fatty acids are unsaturated fatty acid molecules with a trans double bond between carbon atoms. Trans fat molecules tend to be straight, resembling saturated fat molecules. Like saturated fats, the straightness of trans fatty acids allows them to be packed more densely in the body. Research suggests a strong correlation between trans fat consumption and circulatory system disease, including atherosclerosis and coronary heart disease.

Triacylglycerol is a glyceride in which a glycerol backbone is esterified with three fatty acid chains. The three chains can be the same fatty acid, only two the same, or all different. Chain lengths can also vary, with 16, 18 and 20 carbon atoms being most common. Vegetable oils and animal fats are primarily comprised of triglycerides. While the linkage between elevated triglyceride levels and atherosclerosis and coronary heart disease is not well understood, an inverse relationship exists between triglyceride level and HDL (“good”) cholesterol level.


Unsaturated fatty acids.
Fatty acids of similar form, except that one or more alkenyl functional groups exist along the chain, with each alkene substituting a double-bonded carbon for a single-bonded part of the chain. The two next carbon atoms in the chain, bound to either side of the double bond, can occur in either cis or trans configuration. The rigid double bond in an unsaturated fat “kinks” the chain so that spatial storage is less efficient and the melting point is lowered. This explains why vegetable oils, which are comprised of unsaturated fatty acids, are liquid at room temperature.