The Biohacker's Glossary

I usually try to write articles that everyone can easily understand, but moving forward, it will be helpful to know these foundational concepts.

The Basics

• N=1 / Self-experimentation: An experiment with a sample size of one: you. The conclusion is true for you, but not necessarily for anyone else. It is a biohacker's primary tool and, simultaneously, their greatest limitation.
• Baseline: Your metrics in a normal state before any intervention. Without it, you cannot know if something worked because there is nothing to compare it against.
• Biomarker: A measurable indicator of your body's state—such as resting heart rate, fasting glucose, vitamin D, or HRV.
• Placebo: An improvement caused by the mere fact of an intervention rather than its actual substance. The main enemy of N=1: if you expect an effect, you will often "feel" it. This is why objective biomarkers are more reliable than subjective sensations.

Sleep

• Circadian Rhythm: The internal ~24-hour clock that regulates sleep, hormones, body temperature, and metabolism. The main "conductor" is light hitting the retina.
• Melatonin: The hormone that signals to the body that it is time to sleep. It is produced in darkness and suppressed by bright (especially blue) light. It is not a sleeping pill, but a timing signal.
• Sleep Latency: The time it takes to fall asleep. Around 15 minutes is normal; passing out within a minute is more often a sign of sleep deprivation than healthy sleep.

Nutrition and Metabolism

• Intermittent Fasting: An eating pattern where meals are restricted to a specific time window (e.g., 16/8). It works primarily through calorie restriction and metabolic signaling.
• Autophagy: Intracellular "cleanup"—the breakdown and recycling of damaged cellular components. It is accelerated by fasting and exercise. Yoshinori Ohsumi won a Nobel Prize for discovering its mechanisms in 2016.
• Ketosis: A metabolic state where, due to a lack of carbohydrates, the body switches to burning fat and produces ketones to use as fuel.
• Insulin Resistance: A condition where cells respond poorly to insulin, forcing the body to produce more of it. An early step toward type 2 diabetes.
• Metabolic Flexibility: The body's ability to seamlessly switch between fuel sources (carbohydrates ↔ fats). A hallmark of a healthy metabolism.
• Glycemic Response: How high and how fast your blood sugar rises after eating. This is highly individual: the same food can elicit completely different responses in different people.

Activity and Recovery

• VO₂max: The maximum volume of oxygen your body can utilize during intense exercise. It is the power capacity of your "engine" and one of the strongest predictors of longevity.
• Zone 2: Low-intensity aerobic exercise during which you can still hold a conversation. The foundation of endurance and mitochondrial health.
• Mitochondria: The "power plants" of the cell that produce ATP. Their quantity and quality form the basis of endurance and healthy aging.
• Hormesis: "What doesn't kill you makes you stronger" at a cellular level—small, dosed amounts of stress (exercise, cold, heat, fasting) trigger beneficial adaptations.
• Cold and Heat Exposure: Controlled stress via cold or heat (such as a sauna). A specific application of hormesis. In observational studies, sauna use is associated with reduced mortality (a correlation, not a proven cause).

Cognitive Functions

• Nootropics: Substances used to improve memory, focus, and clarity of thought.
• Neuroplasticity: The brain's ability to reorganize its connections in response to experience. This makes learning possible at any age.
• CNS: Central Nervous System.
• BDNF: A protein that supports the growth and survival of neurons, often called "fertilizer for the brain."

Neurotransmitters

Chemical substances used to transmit impulses from nerve cells to other neurons.

• Dopamine: The neurotransmitter of motivation and reward anticipation (rather than a "pleasure hormone"). It explains phone addiction and procrastination.
• Acetylcholine: The neurotransmitter responsible for attention, learning, memory, and muscle contraction. Roughly speaking, it is the "chemistry of focus and retention." Its deficit is linked to Alzheimer's disease, and many nootropics target it.
• Serotonin: A neurotransmitter that influences mood, sleep, appetite, and gut function. It is often referred to as the "happiness hormone."
• Norepinephrine: The neurotransmitter of alertness, concentration, and readiness to act. It heightens attention and tone, playing a key role in the "fight-or-flight" response.
• Epinephrine (Adrenaline): The acute stress hormone responsible for the classic "fight-or-flight" rush. It increases heart rate, raises blood sugar, and mobilizes energy within seconds.
• GABA: The brain's primary inhibitory neurotransmitter, acting as its "brake pedal." It calms and slows down neural activity, serving as a counterweight to glutamate.
• Glutamate: The main excitatory neurotransmitter, acting as the brain's "gas pedal" for learning, memory, and general signaling.

Anandamide and Opioids

The body's internal systems for pleasure and pain relief.

• Anandamide: An endocannabinoid (named after the Sanskrit word ananda, meaning "bliss"). It acts on the same receptors as cannabis and is linked to mood, appetite, and the "runner's high."
• Endogenous Opioids (Endorphins): Internal painkillers and reward molecules. The word "endorphin" literally means "endogenous morphine."

Hormones

Biologically active substances produced by endocrine glands that enter the bloodstream and act as chemical messengers.

• Oxytocin: The hormone of attachment, trust, and social bonding. It is released during hugging, physical touch, intimacy, childbirth, and breastfeeding.
• Cortisol: The primary stress hormone released by the adrenal glands.
• Estradiol: The primary and most active female sex hormone from the estrogen group (also present in men).
• Testosterone: The primary androgen (male sex hormone, though also present in women). It is responsible for muscle mass, bone density, libido, mood, and energy.

Longevity

• Healthspan vs. Lifespan: Lifespan is how many years you live; healthspan is how many of those years you spend in good health. The goal is to extend the latter, not just the former.
• Hallmarks of Aging: A set of fundamental aging processes (DNA damage, cellular senescence, stem cell exhaustion, etc.) that scientists use to mechanistically describe how we age.
• Cellular Senescence: A state where a cell stops dividing but does not die, accumulating and secreting inflammatory signals instead. These "zombie cells" contribute to age-related diseases.
• NAD⁺: A molecule critical for energy production and DNA repair; its levels decline with age. This drives the popularity of precursors like NMN and NR (though human data remains limited).

Supplements

• Bioavailability: The fraction of a substance that successfully reaches its intended site of action. A massive dose on the label does not equate to a significant effect if very little is absorbed.
• Stack: A combination of supplements or compounds taken together.
• Adaptogens: Plants or substances (like ashwagandha and rhodiola) believed to help the body adapt to stress. The quality of scientific evidence varies.

Tracking

• CGM (Continuous Glucose Monitor): A sensor that measures blood sugar levels in real time. It shows your personal glycemic response to specific foods.
• Wearables: Rings, watches, and bands that track sleep, heart rate, HRV, and physical activity. Their accuracy is not perfect, but tracking their trends over time is highly useful.