performance glossary

Glossary

AA Arachidonic acid (aka arachidonate). A 20-carbon omega-6 essential fatty acid that provides vital physical properties to all cellular membranes, as well as serving as substrate for a myriad of oxylipids (eicosanoids) with hormonal and signaling functions. A common reductionist perspective labels AA as ‘pro-inflammatory’ and thus ‘bad’. A more cosmopolitan view recognizes that AA is vital for many membrane functions (including insulin action), whereas it only can become ‘pro-inflammatory’ when released from membrane PL by specific phospholipase enzymes.
AcAc Aceto-acetate. One of two ketones produced from fatty acids by the liver. Usually converted to BOHB in muscle before being taken up and oxidized for energy by the brain.
ATP Adenosine tri-phosphate. This high energy phosphate is, along with creatine phosphate, the body’s source of instant cellular energy. The release of one phosphorus produces adenosine di-phosphate (ADP), a free phosphorus molecule, and energy to power a host of functions including muscle contraction. Either glycolysis or oxidative phosphorylation can then re-attach a phosphorus to ADP, recreating the ATP energy charge.
BCAA Branched chain amino acids. These consist of leucine, iso-leucine, and valine. Chemically, these three amino acids can be regarded as short-chain fatty acids with an amino group attached. Once the amino group is detached (the first step in their breakdown), they can burned for energy in mitochondria like any other short-chain fatty acid such as pyruvate or BOHB.
BMI Body mass index. This is calculated by dividing one’s weight in kilograms by the square of one’s height in meters. Values for adults between 18 and 25 are considered normal (aka healthy), 25-30 overweight, and above 30 is classified as obese. BMI is not a measure of body composition, but on average for large groups of subjects, BMI correlates well with body fat content. For individuals, however, BMI often correlates poorly with direct measures of adiposity, as for example in power athletes with expanded lean body mass.
BOHB Beta-hydroxy butyrate. One of two ketones produced from fatty acids by the liver. The preferred ketone fuel to support the brain’s energy needs.
CO2 Carbon dioxide. Produced by the oxidative metabolism of glucose, fats, and amino acids. Its content in the blood is one of the two major drivers of respiration (along with blood oxygen content).
CVD Cardiovascular disease. A combination of plaque formation in coronary vessel walls, plus hemorrhage into unstable plaques and thrombus (clot) formation that block blood flow to the heart muscle.
DHA Docosahexaenoic acid. A 22-carbon omega-3 essential fatty acid found in human cell membranes, particularly in the central nervous system and the retina of the eye. Typically DHA is 10-fold more prevalent in human membranes than its metabolic precursor EPA (and 100-fold more so in the eye). Typically, the metabolic functions of DHA counter-balance those of AA, although in some membrane functions (such as insulin sensitivity) they are complementary.
DRI Daily reference intake. This is a broad system used by the United States and Canada to develop recommendations for macronutrient and micronutrient intakes. It encompasses recommended dietary allowances (RDA), adequate intake (AI) and tolerable upper intake levels (UL). DRIs are relevant for healthcare policy and public health; they do not address individual circumstances and needs. Personal nutrient requirements may be higher or lower.
DXA Duel energy x-ray absorptiometry (also called DEXA). Originally developed to accurately measure bone density, this technique is now available to measure body composition, including regional fat distribution. It uses a pair of x-ray beams of differing energies to measure tissue density. Because of the very narrow beams, the x-ray dose from this procedure is inconsequential compared to normal background radiation.
EFA Essential fatty acid. These consist of two classes (omega-6 and omega-3) of 18- to 22-carbon polyunsaturates that serve both structural (membrane) and vitamin-like functions in humans.
EPA Eicosapentaenoic acid. A 20-carbon omega-3 essential fatty acid. EPA represents about 50% of the omega-3 fatty acids found in most ‘fish oil’, but is typically between 1-10% of omega-3 fatty acids in human membranes. Because EPA directly antagonizes the pro-inflammatory effects of arachidonate, however, it is touted for its pharmacological properties. If this were true from a global perspective, however, most of the EPA we eat wouldn’t be promptly converted to DHA. Go figure.
HUFA Highly unsaturated fatty acids. This term refers to fatty acids of 20-carbon or longer chain length containing three or more double bonds. Most are from either the omega-6 or omega-3 classes, although the non-essential omega-9 biomarker of EFA deficiency (Mead acid – 20:3n-9) is also included in this classification.
Kcal Kilocalorie, also referred to as ‘Calorie’. A kilocalorie or Calorie (spelled with a capitol ‘C’) is approximately the amount of heat needed to raise the temperature of one liter of water by one degree Celsius. A ‘calorie’ is one one-thousandth this amount. While the use of the kilocalorie unit persists in North America, most of the rest of the world uses the SI unit ‘joule’ – there are 4.18 kilojoules (kJ) per kcal.
LCT Long-chain triglycerides. Typical dietary fats in which the three individual fatty acids attached to the glycerol backbone have 14 or more carbons (and usually either 16 or 18 carbons). Absorption from the gut is via chylomicrons that enter the circulation via the lymphatics and the thoracic duct.
MCT Medium-chain triglycerides. Triglyceride molecules in which all or most of the fatty acids attached to the glycerol backbone have 8-12 carbons and no double bonds. Absorption from the gut is followed by secretion into the portal vein and delivery to the liver, where most MCT are oxidized or made into ketones.
MP-EFA Membrane phospholipid essential fatty acids. Phospholipids have a polar end (‘likes water’) and a non-polar lipid end (‘hates water’). When mixed in water, they align their non-polar ends, leaving the polar ends out towards the water. This spontaneously generates the classic lipid bi-layer membrane structure upon which all cellular life depends. Most phospholipid molecules have two fatty acids attached to the glycerol backbone. Of these, one is usually a saturated fat and the other one a polyunsaturated fat of either the omega-6 or omega-3 class.
MUFA Monounsaturated fatty acid. A long-chain fatty acid containing one double bond. In plant and mammalian metabolism, the predominant monounsaturate is the 18-carbon oleic acid (found in olive oil, high oleic safflower oil, lard, oolichan grease, and human adipose tissue).
O2 Oxygen
OFM Optimized Fat Metabolism is a ultra-endurance performance strategy developed by Peter Defty that integrates diet/fueling, training, rest/recovery, and lifestyle with the all-natural supplement, VESPA, to make a fundamental physiological shift to metabolizing fat as the primary and preferred aerobic energy source. OFM challenges the conventional carbohydrate centric approach toward athletic performance and human health, using cutting edge nutritional and physiological science to help guide the program. OFM does not completely eliminate carbohydrates, but makes “strategic” use of specific sources of carbohydrates before and during ultra-events. Thus, while OFM is NOT necessarily a low-carb diet per se, many principles used in OFM are taken from research done on low-carbohydrate dietary regimens, including the concepts of nutritional ketosis and keto-adaptation.
PEPCK Phosphoenolpyruvate carboxykinase. PEPCK is a key enzyme in gluconeogenesis (the pathway by which glucose is formed from non-carbohydrate sources). Fascinating work has shown that genetically modified animals that over-express this enzyme in skeletal muscle are leaner and more active.
pH This is a measure of the concentration of free hydrogen in water. Pure water has a pH of about 7 (neutral). Values below 7 indicate acidity, and those above 7 indicate alkalinity. Technically, pH is the negative logarithm of the molar concentration of dissolved hydronium ions (H3O+).
PL Phospholipid. A complex mix of amphloteric compounds that form into surfaces at lipid/water interfaces. Membranes contain a mix of PL, proteins, and free cholesterol. In human membranes, PL are typically enriched with HUFA relative to other fatty acid pools like adipose TG.
PUFA Polyunsaturated fatty acid. Long-chain fatty acids that contain two or more double bonds. PUFAs carry a positive connotation because they have been shown to lower total serum cholesterol. Unfortunately it is lost on most observers that this occurs at the expense of HDL cholesterol (aka ‘good’ cholesterol), thus doing potentially as much harm as good. More PUFA (particularly HUFA) in membranes is good, but more PUFA in the diet (particularly in the context of a high fat diet) is more than likely bad. The major determinant of how much PUFA or HUFA you have in your membrane appears to be more a function of how slowly you destroy them rather than how much of them you eat.
ROS Reactive oxygen species. Also called oxygen free radicals or free radicals. Typically oxygen-containing small molecules with a single free electron in the outer shell. These combine chemically with unsaturated fatty acids or proteins, and frequently create additional free radicals in a cascade-like reaction. This process is referred to as oxidative stress, and is countered by multiple enzymes and anti-oxidants that quench this reaction.
RQ Respiratory quotient. The ratio of the minute volumes of CO2 produced divided by O2 consumed (VCO2/VO2). Technically, this ratio uncorrected for protein metabolism is called the ‘respiratory exchange ratio’ (RER), however the two values are very similar and the terms tend to be used interchangeably. Glucose ‘burns’ in the body with an RQ of 1.0 and fat at 0.7. Ketogenesis (making more ketones that are being oxidized) reduces the RQ value, whereas lipogenesis raises it.
SFA Saturated fatty acid. This is a fascinating but much maligned category of fats. In human tissue, these generally range from 14- to 22-carbons in length with no double bonds. Lacking double bonds, saturated fats have higher melting points than unsaturated fats of comparable chain length – thus their tendency to be solid at room temperature (like butter, tallow, and lard). The lack of double bonds also makes them far less prone to peroxidation (i.e., damage by oxygen free radicals) compared to monounsaturates and polyunsaturates, imparting greater stability both within living tissue and as longer shelf-life of foods containing them.
SOD Super oxide dismutase. A family of enzymes in and around mitochondria that quench (neutralize) reactive oxygen species.
VO2 The volume of oxygen consumed per minute, whether at rest or during exercise. This value can be expressed as total use by the whole body, or per kilogram of body weight.
VO2max The peak rate of oxygen consumed during a specific exercise. Typically this occurs as a plateau in oxygen consumption as exercise intensity is increased, and usually associated with an RQ (RER) value >1.0. In keto-adapted subjects, however, VO2max is often reached at RQs less than 1 due to reduced anaerobic lactate production. VO2max can be expressed as a value for the individual as a whole (e.g., 3.5 liters per minute) or per kg of body weight (e.g., 50 ml/kg/min for a 70 kg individual).