Longevity glossary: every buzzword, defined and graded

Every term here gets the same five questions: what it means, why it matters for longevity, what the evidence says (human trials, cohorts, or mice only), how you measure it or use it, and what it is related to. Entries are short on purpose — most are a five-minute read — and each one links out to the longer longevity articles, the research library, the therapies and the guides where the detail lives.

If a term is a marker, the entry says what a good number looks like and how often to check it. If it is a compound, the entry says what it has been studied for and in whom — and nothing more. If it is mostly hype, the entry says that too.

Jump to: A · B · C · D · E · F · G · H · I · L · M · N · O · P · Q · R · S · T · U · V · Z

The terms, A to Z (69)

A

• Acarbose — An alpha-glucosidase inhibitor that slows carbohydrate digestion; extended lifespan in male mice in the ITP, with a plausible glucose-spike mechanism.
• AMPK — AMP-activated protein kinase — the cell's low-fuel sensor; switches on fat burning and repair when energy runs short. Activated by exercise and metformin.
• ApoB — Apolipoprotein B — one per atherogenic particle, so it counts the LDL, VLDL and Lp(a) particles that cause plaque; the lipid number that matters most.
• Autophagy — The cell's recycling programme — damaged proteins and organelles are broken down and reused. Rises with fasting and exercise, falls with age.

B

• Biological age — An estimate of how old your body is functioning, as opposed to how many birthdays you have had.
• Blue Zones — Five regions — Sardinia, Okinawa, Ikaria, Nicoya, Loma Linda — reported to have unusually many centenarians; the lessons are real, the data are contested.

C

• Caloric restriction — Sustained reduction of calorie intake (typically 10–30%) without malnutrition — the oldest and most reproducible lifespan intervention in animals, tested in humans in CALERIE.
• Cellular senescence — A state in which damaged cells stop dividing but refuse to die, secreting inflammatory signals that age the tissue around them.
• CGM (continuous glucose monitor) — A sensor worn on the arm that reads interstitial glucose every few minutes — a two-week window onto how food, sleep and stress move your blood sugar.
• Circadian rhythm — The roughly 24-hour internal clock, set mainly by light, that times sleep, hormones, body temperature and metabolism.
• Cold exposure — Deliberate cold — plunges, showers, cryotherapy — that raises noradrenaline and brown-fat activity; good for mood and alertness, bad after strength training.
• Cortisol and the HPA axis — The hypothalamic-pituitary-adrenal stress system and its main hormone; essential in pulses, damaging when flat, high or inverted.
• Creatine — The best-evidenced sports supplement; 3–5 g/day of creatine monohydrate supports strength, lean mass and, in older adults, possibly cognition and bone.

D

• DEXA scan — Dual-energy X-ray absorptiometry — a low-dose scan that measures bone density, lean mass, fat mass and visceral fat by region.
• DunedinPACE — A methylation clock that reports the pace of ageing — biological years per calendar year — rather than an accumulated age.

E

• Epigenetic clock — A biological-age estimate read from DNA methylation patterns — Horvath, GrimAge, DunedinPACE and others.
• Estradiol in men — The main oestrogen, made from testosterone by aromatase; men need it for bone, libido and fat regulation, and both low and high levels cause problems.
• Exosomes — Nano-sized vesicles released by cells that carry proteins and RNA between them; sold in clinics for "regeneration" with no approved use and almost no controlled human data.

F

• Fisetin — A flavonoid from strawberries with senolytic activity in mice; several human trials are underway, none has reported clear benefit.

G

• GIP — Glucose-dependent insulinotropic polypeptide — the second incretin hormone; combined with GLP-1 in tirzepatide for greater weight loss.
• GLP-1 — Glucagon-like peptide-1 — a gut hormone that boosts insulin, slows gastric emptying and reduces appetite; the target of semaglutide and the dual/triple agonists.
• Glucagon receptor agonist — The third arm of the "triple agonist" drugs: glucagon signalling raises energy expenditure and liver fat burning, adding to GLP-1 and GIP.
• Glycine — The simplest amino acid; a glutathione precursor and sleep aid at 3 g, with a lifespan result in mice and the GlyNAC trial in older adults.
• Grip strength — Hand-grip force measured with a dynamometer — a cheap proxy for whole-body strength that predicts mortality better than blood pressure.
• Growth hormone secretagogue — A compound that prompts the pituitary to release its own growth hormone — GHRH analogues (CJC-1295, tesamorelin) and ghrelin mimetics (ipamorelin, MK-677).
• Gut microbiome — The trillions of bacteria and other microbes in the gut, whose diversity and metabolites shape immunity, inflammation, metabolism and drug response.

H

• HbA1c — Glycated haemoglobin — the share of red-cell haemoglobin with glucose attached, reflecting average blood sugar over about three months.
• HBOT (hyperbaric oxygen) — Breathing 100% oxygen at 1.5–3 atmospheres in a pressurised chamber; a licensed treatment for specific conditions, and a longevity claim built on one small study.
• Healthspan — The years lived in good health, free of serious disease, frailty or dependence — as distinct from lifespan.
• Heat shock proteins — Protective chaperone proteins induced by heat and other stresses that refold damaged proteins — the mechanism behind sauna's benefits.
• HIIT — High-intensity interval training — short bursts near maximal effort with recovery between; the fastest way to raise VO2max.
• HOMA-IR — A calculated index of insulin resistance from fasting glucose and fasting insulin; under 1.0 is ideal, over 2.0 flags resistance.
• Hormesis — The principle that a small dose of a stressor — heat, cold, exercise, fasting — triggers an adaptive response that leaves the organism stronger.
• HRV (heart rate variability) — The beat-to-beat variation in heart rhythm — a proxy for autonomic balance and recovery; higher is generally better, and the trend matters more than the number.
• hs-CRP — High-sensitivity C-reactive protein — the standard blood marker of low-grade chronic inflammation; under 1 mg/L is the target.

I

• IGF-1 — Insulin-like growth factor 1 — the liver hormone that mediates growth hormone's effects; a two-sided marker, with both low and high levels linked to worse outcomes.
• Inflammaging — The chronic, low-grade, sterile inflammation that rises with age and drives cardiovascular disease, sarcopenia, insulin resistance and frailty.
• Insulin resistance — A state in which muscle, liver and fat respond poorly to insulin, so the pancreas makes more; the root of most metabolic disease and a driver of ageing.

L

• Lifespan vs healthspan — Lifespan is how long you live; healthspan is how long you live well. The gap between them is the target.
• Longevity escape velocity — The speculative point at which medicine adds more than a year of life expectancy per year lived — a thought experiment, not a forecast.
• Lp(a) — Lipoprotein(a) — a genetically set, LDL-like particle that raises heart-attack and aortic-stenosis risk; test once, since diet barely moves it.

M

• Metformin — A first-line diabetes drug that activates AMPK and lowers hepatic glucose output; studied for longevity in the TAME trial, with a known trade-off against training adaptation.
• mTOR — Mechanistic target of rapamycin — the nutrient-sensing kinase that drives growth when fuel is plentiful and, when chronically on, accelerates ageing.
• Muscle protein synthesis (MPS) — The process of building new muscle protein, triggered by resistance training and by about 2.5–3 g of leucine per meal.

N

• NAD+ — Nicotinamide adenine dinucleotide — the coenzyme every cell uses for energy metabolism and DNA repair; declines with age, raised by precursors with uncertain benefit.
• NMN — Nicotinamide mononucleotide — a direct NAD+ precursor; raises blood NAD+ reliably, with small human trials and modest results.
• NR (nicotinamide riboside) — A form of vitamin B3 that raises blood NAD+; the best-trialled NAD+ precursor, with consistent NAD+ increases and few functional changes.

O

• Omega-3 index — The percentage of EPA + DHA in red-blood-cell membranes; below 4% is high risk, above 8% is the target.

P

• Peptides — Short chains of amino acids (under about 50) that act as signalling molecules — insulin, GLP-1 and growth hormone are peptides; so are most research compounds.
• Photobiomodulation — Red and near-infrared light (600–1,000 nm) applied to tissue to stimulate mitochondrial activity — the clinical name for red-light therapy.
• Protein leverage — The hypothesis that appetite is driven by a protein target: when protein is diluted, you overeat calories until the protein need is met.

Q

• Quercetin — A flavonoid in onions and apples; part of the dasatinib + quercetin senolytic combination, with weak evidence on its own.

R

• Rapamycin — An mTOR inhibitor and transplant drug; the most reproducible lifespan extender in mice, used off-label at low intermittent doses by some longevity physicians.
• Resveratrol — The red-wine polyphenol marketed as a sirtuin activator; strong cell-culture story, weak and inconsistent human trials.

S

• Sarcopenia — Age-related loss of muscle mass and strength — a recognised disease since 2016, and the main road to frailty and dependence.
• Senolytics — Drugs or compounds that selectively kill senescent cells — dasatinib plus quercetin, fisetin, navitoclax — with strong mouse data and early human data.
• SHBG — Sex hormone-binding globulin — the liver protein that binds testosterone and estradiol; it decides how much hormone is free, and tracks insulin resistance.
• Sirtuins — A family of NAD+-dependent enzymes (SIRT1–7) that regulate DNA repair, metabolism and stress responses — the pathway behind the resveratrol and NMN story.
• Sleep architecture — The structure of a night's sleep — cycles of light, deep (slow-wave) and REM sleep — and how the proportions change with age.
• Spermidine — A polyamine found in wheat germ, soy and aged cheese that induces autophagy; extends lifespan in mice, with human cohort data and one small cognition trial.
• Stem cells — Undifferentiated cells that can renew themselves and become specialised cell types; licensed for blood cancers, experimental for almost everything else sold under the name.

T

• Taurine — An amino sulfonic acid that falls with age and extended lifespan in mice and monkeys in a 2023 study; human data are observational only.
• Telomeres — Protective caps on chromosome ends that shorten with each cell division — a marker of cellular ageing, not a lever.
• Time-restricted eating — Confining all meals to a daily window of 8–10 hours, aligned with daylight; the most sustainable form of intermittent fasting, with modest metabolic effects.
• TRT — Testosterone replacement therapy — prescribed testosterone for men with symptomatic, lab-confirmed deficiency; the TRAVERSE trial settled cardiovascular safety.

U

• Urolithin A — A gut-microbiome metabolite of pomegranate ellagitannins that induces mitophagy; two placebo-controlled human trials show modest muscle-endurance gains.

V

• Visceral fat — Fat stored around the abdominal organs rather than under the skin; metabolically active, inflammatory, and the fat depot that predicts disease.
• VO2max — Maximal oxygen uptake — the ceiling of your aerobic engine, in ml/kg/min; the single strongest measurable predictor of how long you live.

Z

• Zone 2 training — Steady aerobic exercise at an intensity where you can still speak in sentences — the base-building work that grows mitochondria and fat-burning capacity.

How to use the glossary

• Start with the markers. ApoB, Lp(a), HbA1c, HOMA-IR, hs-CRP, VO2max and grip strength are the handful of numbers that explain most of the variance in how people age — and all are measurable this month.
• Read the mechanism terms as background, not as targets. mTOR, AMPK, sirtuins, autophagy and NAD+ are real biology; none of them is something you can see on a lab report or should chase with a supplement stack.
• Compounds get evidence grades, not promises. Rapamycin, metformin, NMN, spermidine, fisetin: the entries say which have human trials with hard outcomes (few) and which are mice only (most).
• Then turn it into a plan. The longevity protocol article shows how the terms become a sequence, and the baseline labs guide shows which to draw first.