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Calorie Restriction Glossary

Arachidonic Acid

A transport chemical which functions similarly to carnitine but more effectively and efficiently.

ad lib or Ad Lib
Short for the latin term "ad libitum" meaning "at will". In the context of CR experiments, it refers to the diet of the control group. If taken literally it means the control group was given free and continuous access to food, and allowed to eat as much as they wanted. In more recent CR experiments, researchers have modified this strategy by feeding the control group a minorly restricted diet in order to prevent obesity. The CR group is usually fed some percentage of the calories eaten by the ad lib group.

Advanced Glycation Endproducts
Modified proteins proposed to contribute to pathologies associated with diabetes and aging. Formed by the nonenzymatic reaction of proteins with sugars. AGEs accumulate with age and represent a form of macromolecular damage. Intermolecular cross-linking leading to insolubility is one feature of some AGEs.

All Else Being Equal

As Far As I Know

Advanced Glycation Endproducts

Ad Libitum or Ad Lib for short

An ambiguous acronym, sometimes referring to Alpha Linolenic Acid, and sometimes referring to Alpha Lipoic Acid.

Shorthand name for a famous post to the CR Society email list by Michael Rae in which he presented lots of evidence about the optimal macronutrient ratio for people in general, and for CR practitioners in particular. It is available in the archives here: http://lists.calorierestriction.org/cgi-bin/wa?A2=ind0009&L=crsociety&P=R2

Alpha Linolenic Acid
An omega-3 fatty acid. The best source is flax seed and flax seed oil.

Alpha Lipoic Acid
An anti-oxidant. Comes in R- and S- form. Some evidence suggests the R- form may be better.

General term for sex hormone. Examples include testosterone and estrogen.

(1) A molecule capable of accepting an electron from an ROS, neutralizing it and halting the associated negative chain reaction. (2) A compound or agent capable of preventing or reversing the creation of Reactive Oxygen Species (ROSs) or "free radicals". Examples are too numerous to list exhaustively, but include some vitamins such as vitamin E and C.


Arachidonic Acid
An omega-6 fatty acid.

As soon as possible

Weight loss diet guru who advocates a diet relatively low in carbohydrates and high in fat.

The energy storage molecule all cells use to perform useful work. Generated by mitochondria.

A negative feedback system which buffers short-term changes in blood pressure. It allows a person to avoid fainting upon rising due to a sudden drop in blood pressure.

Basal Metabolic Rate
A measure of calories burned while at rest.

Body Fat

Blood Glucose

Bone Mineral Density

Body Mass Index. A height-independent measure of relative weight. (704 * weight) / (height * height), where weight is in lbs and height is in inches (also, weight-in-kilograms divided by height-in-meters squared).

Basal Metabolic Rate

Blood Pressure

Brown Fat
A type of fat abundant in rodents but scarce in people. Responsible for much of the heat generated by rodents.

By The Way

Blood Urea Nitrogen

Formally defined in scientific circles as the amount of energy required to raise the temperature of one gram of water one degree Celsius. But this is a very small amount of energy, so the scientific definition of calorie is usually not used when talking about the energy content of food. Instead, a food "Calorie" usually refers to one kilocalorie. One calorie is equivalent to 4.18 joules (another unit of energy) and one Calorie (capital "C") is equivalent to 4180 joules or 4.180 kilojoules.

Calorie Restriction
Eating fewer calories while achieving adequate or optimal nutrition. It is the one intervention that has been shown to extend both mean and maximum lifespan in all species tested to date.

A transport chemical required for passage of fatty acids through membranes of mitochondria. Synthesized by mammals, carnitine can also be absorbed from ingestion of meat, dairy products, and supplements.

Coronary Heart Disease - a disease of the heart and/or blood vessels in which the flow of blood is obstructed. Used synonymously with cardiovascular disease.


Coenzyme Q-10
A mitochondrial coenzyme, used to shuttle electrons through the electron transport chain, and a potent antioxidant.

A calorie restriction regime which is 25% below ad-lib calorie intake.

Calorie Restriction with Adequate Nutrition

Calorie Restriction with Optimum Nutrition

CRonie or CRONer.
Slang: A tongue-in-cheek term for a CR practitioner.

Cross-over Design
A scientific study in which the conditions are flipped partway through the experiment. For example, if group A received a particular drug during the first part of an experiment, and group B received a placebo, then in the second part of the experiment the groups would be "crossed-over", meaning group A will receive the placebo and group b will receive the drug. Facilitates more reliable statistical analysis by allowing subjects to act as their own controls.

Cardiovascular disease -- a disease of the heart and/or blood vessels in which the flow of blood is obstructed. Used synonymously with coronary heart disease.

Delta-5 desaturase enzyme

Delta-6 desaturase enzyme

Dihomogamma linolenic acid, an omega-6 fatty acid.

Docosahexaenoic acid, an omega-3 fatty acid. Richest source is fatty fish and fish oil.

Dehydroepiandrosterone (Sulphate). DHEA and DHEAS are weak male directed hormones secreted by the adrenal gland. In high doses, they can be converted by the liver into sex hormones such as testosterone and estrogen. In non-CR people, blood levels of this hormone peaks around age 25 and gradually declines to virtually zero by ago 70.

Docosahexaenoic Acid
An omega-3 fatty acid

Essential Amino Acid. Protein is composed of these (and other) amino acids.

A short-lived, short-range hormone (roughly speaking).

Eicosapentaenoic Acid
An omega-3 fatty acid. Richest source is fatty fish and fish oil.

Every Other Day. Usually in reference to the feeding pattern of animal in some CR studies, where they are provided access to food only alternating days. A form of fasting.

Energy Restriction. Sometimes used interchangeably with CR, although CR is virtually always associated with a diet restricted in calories, but not lacking in nutrition. In contrast, an energy-restricted diet can sometimes mean simply mean feeding the subjects less of the same food, which could result in nutritional deficits.

Essential Fatty Acid
A building block of the body that the human body cannot itself make. They are either omega-3 or omega-6 fatty acids.

Electron Transport System. The process by which cells, and specifically mitochondria, convert energy in food to a useable form (ATP) for work.

Food Restriction. Sometimes used interchangeably with CR however FR does not always imply a nutritionally adequate diet as CR does.

A human hormone

For Your Information

Growth Hormone

Glycemic Index, or Gastro-Intestinal.

Gamma Linolenic Acid, an omega-6 fatty acid.

A chemical reaction that link a sugar to a protein or peptide. If not undone, such a reaction can lead to the formation of an Advanced Glycation Endproduct (AGE).

Glycemic Index
Measures the impact that a food has on blood glucose levels. Glucose is considered to have a glycemic index of 100. Note that there do exist foods (e.g., dates) which have a glycemic index greater than 100.

Glycosylated Hemoglobin
The result of glycation of a sugar with hemoglobin in the blood. Also called glycohemoglobin, or HbA1c. It is used as a common marker for AGE accumulation. Elevated in diabetics, and others eating a high GI diet.

Glycosylated Hemoglobin


Hemaglobin. The oxygen carrying molecule in the blood.

Human Growth Hormone

An amino acid used normally by the body in cellular metabolism and the manufacture of proteins. Elevated concentrations in the blood are thought to increase the risk for heart disease by damaging the lining of blood vessels and enhancing blood clotting.

An effect in which a toxic substance acts like a stimulant in small doses, but it is an inhibitor in large doses.

High oleic sunflower oil -- YABA.

Highly unsaturated fatty acid. Example: DHA.

High blood pressure

Low blood pressure

Inositol Hexanicotinate

If I Recall Correctly

In My Humble Opinion

In My Opinion

In Vitro
A biological study is one which is carried out in isolation from a living organism (in contrast to In Vivo studies).

In Vivo
A biological study which takes places within a living biological organism (as opposed to an In Vitro study).

A hormone critical for metabolizing glucose. But to high levels of insulin, commonly associated with Type II diabetes, is thought to have very negative health consequences.

Intrinsic Aging Rate
A technical term referring to the rate of aging of an organism, which is independent of the specific age-associated disease to which the organism eventually succumbs. In other words, as an organism gets older, it becomes more susceptible to a wide range of potential killers -- in some sense more "fragile". It is this rate of increase in susceptibility with time that is referred to as the intrinsic aging rate. Often quantified using the MRDT measure.

Equivalent to 1000 calories in the formal definition of the term calorie. Kcal is the amount of energy commonly referred to as a "Calorie" when speaking of the energy content in food.

Linoleic Acid - An essential omega-6 fatty acid.

Life Extension

Protein found in many grains, rice and legumes which can disrupt cell membranes and may initiate a cascade of immune and autoimmune events leading to cell death.

Luteinizing hormone -- stimulates the production of testosterone in male testes.

Alpha Linolenic Acid

Laughing Out Loud


One of the three primary categories of nutrients in food -- fat, protein or carbohydrate.

Maximum Lifespan
The maximum age to which a species or member of a group can be expected to live. It is typically estimated experimentally as the average age of death of a small fraction (e.g. 5%) of a population or group. There is an important distinction to be made between extending the "maximum lifespan" of a particular study group (as defined above, relative to controls in the same study) vs extending the species maximum lifespan (the maximum age to which normal, well cared-for members of the species live). For former has been shown to result from a number of interventions (e.g. fish oil supplements in autoimmune-prone mice), but CR is the only intervention known to consistently extend species maximum lifespan. See also: mean lifespan.

Mean Corpuscular Hemoglobin

Microcrystalline Hydroxyapatite

Mean Corpuscular Hemoglobin Concentration

Mean corpuscular volume. Size of red blood cells.

Mean Lifespan
The average age of death of a population. See also maximum lifespan.

An online US Government index of abstracts of medical papers. Also referred to as PubMed. Here is the link to search Medline/PubMed.

Microcrystalline Hydroxyapatite
Bone-extracted calcium. Very bioavailable, making it a good form of calcium supplement.

Mitochondrial Free Radical Theory of Aging

Mitochondrial Inner Membrane

Mitochondrial Intermembrane Space

Mitochondrial Inner Membrane
Where the ETS is located.

Mitochondrial Intermembrane Space
The space between the inner and outer mitochondrial membranes, where the protons get pumped.

Manganese-based superoxide dismutase -- the only SOD which works in the mitochondria. Not present in the mitochondrial intermembrane space.

Mortality Rate
The probability that a given individual (or member of a population) will die (from any cause) within a given time period (e.g. one year). See entry for mortality rate doubling time for the relationship between mortality rate and aging.

Mortality Rate Doubling Time


Monounsaturated fatty acid. Rich sources include olive oil, hazelnuts, almonds and avocados.



Nota bene -- latin for "note well". Used to call particular attention to something.

Non-Insulin Dependent Diabetes Mellitus. Type II diabetes, the kind associated with obesity, and not the insulin dependent kind which is typically genetic.

None Of The Above

Optimal Daily Allowance. Optimal, as opposed to recommended daily allowance.

Omega-3 Fatty Acid
A fatty acid. The "3" describes the structure of the fat molecule. It is generally accepted that most people get too many omega-6 fatty acids compared to their omega-3 intake.

Omega-6 Fatty Acid
An essential fatty acid. See the description of omega-3 fatty acid.

Odds Ratio. The probability of one group exhibiting a particular outcome compared with another group. For example, if the CR group had an odds ratio of 0.6 of getting stomach cancer relative to the AL-fed group, that would mean the CR group was only 60% as likely to get stomach cancer.

Oxygen Radical Absorption Capacity. A measure of how good a food is at scavenging ROSs.

Ornish, Dean
Diet guru who advocates a diet relatively high in complex carbohydrates such as fruits, vegetables, and whole grains, low in fat, and low in simple carbohydrates such as sugar and white flour.

A substance which is naturally present in the body and essential to its health. Orthomolecules are substances which have to be in the human body by its very design, whether it comes from without (essential nutrients, air), or within (endogenously-synthesized stuff like R-LA or insulin).

On The Other Hand

Oxidative Stress
A state of imbalance in the body in which Reactive Oxygen Species (ROSs) or "free radicals" are formed. Usually results when prooxidants dominate over antioxidants. Defense against oxidative stress depends primarily on an orchestrated synergism between several endogenous and exogenous antioxidants.

A chemical reaction that creates a peroxide. A peroxide is defined as an oxide that contains more oxygen than some other oxide of the same element (e.g., compare water (h1O) and hydrogen peroxide (h1O2)). Thus, to peroxidize is to oxidize to the greatest possible degree. Lipid peroxidation alters fat molecules within the body, usually with negative consequences.

Platelet (count)

Compound or agent capable of generating Reactive Oxygen Species (ROSs) or "free radicals". An example is iron.

Prospective Study
A study in which a population is identified ahead of time, and then followed for a period of time to see the result of their particular behavior. For example, in a prospective study, one might identify tofu eaters, and then follow them as well as a similar group of non-tofu eaters for many years to determine what if any differences there are in the health of the two populations.

An online US Government index of abstracts of medical papers. Also referred to as Medline. Here is the link to search Medline/PubMed.

Poly-unsaturated Fatty Acid

R-lipoic Acid
A shorthand term used here and there on the list to mean the R- form of alpha lipoic acid.

Red Blood Cell

Respiratory Control Index

Red Cell Distribution Width

Recommended Daily Allowance
Guidelines established by the United States Food and Drug Administration (presumably) describing nutrient levels that agency believes to be "good".

Respiratory Control Index
The ratio of state 3 to state 4 mitochondrial activity. A (somewhat artificial) means of measuring the amount of energy from calories metabolized that is going to generate useful work/ATP (state 3) vs. thermogenesis (state 4). Can be thought of as a measure of "metabolic efficiency".

Resting Metabolic Rate -- synonymous with Basal Metabolic Rate

Reactive Oxygen Species, more popularly known as "free radicals". Molecules with one too few electrons. They strip electrons from other molecules in the body, damaging the other molecules in the process. The molecule that gets stripped then becomes a ROS, and a negative chain reaction commences. It is this type of chain reaction that is thought is commonly believed to underlie the process of aging and many diseases.

Standard American Diet

Set Point
"...that weight toward which one naturally drifts." [Walford, _B120YD_].

Sex hormone-binding globulin. Ties up androgens like testosterone, preventing them from being biologically active.

Standard Metabolic Rate or Standard Mortality Rate

A brand of scale that not only measures weight, but also percentage of body fat using an electrical impedance method. A tool commonly used among people practicing CR. See http://www.tanita.com/ for details.

Sex hormone found most abundantly in men. Often seen to be reduced by CR.

The process of generating heat.

Hibernation-like state in animals in which thermogenesis decreases and body temperature drops. Torpor is facilitated by CR. May be related to the lifespan benefits of CR.

Uncoupling Protein
A family of proteins that are embedded in the MIM, and that allow for the leakage of protons back into the mitochondria and in the process generating heat (thermogenesis), without producing useful work (ATP).

Uncoupling Protein 3
An uncoupling protein in muscle cells as well as brown fat, UCP-3 uncouples the ETS, making the MIM leakier.

Maximal oxygen consumption during exercise. Considered to be the single best measure of cardiovascular fitness. VO2max declines with age. A low VO2max score has been shown to be one of the best predictors of all cause mortality in people.

White blood cell. WBC levels are often seen to drop in animals and people subject to CR, despite improvements in the immune system function.

Wheat Germ Agglutinin. Wheat germ agglutinin may be considered a "bad" lectin.

With Respect To

Your Mileage May Vary

A popular diet advocated by Barry Sears. One primary tenet is achieving the right macronutrient ratio at every meal/snack to balance eicosanoids. The general ratio is 30% of calories from protein, 30% of calories from fat and 40% of calories from carbohydrates -- but Sears says these ratios should be tailored to the individual. The Zone diet also focuses on getting most fat calories from MUFA.