The Health & Longevity Series
Medical education on how the body works, organized by health topic and by program, so you know what to ask before you speak to a physician.
Metabolic health3 min readMetabolic health: glucose, lipids, blood pressure and weight
What metabolic health means, the measures physicians read, and the everyday factors that shape it.
Sleep3 min readSleep physiology: rest, energy, mood and metabolism
What the body does during sleep, how it is tied to energy, mood and metabolism, and what disturbs it.
Healthy aging3 min readThe biology of healthy aging and healthspan
What aging is at the level of the cell, why its pace differs, and the ordinary things that matter most.
Focus3 min readCognitive focus and mental energy
How attention works, what it depends on, and the common, checkable reasons concentration dips.
Hormone health3 min readEndocrine health: how hormones regulate the body
How hormones are controlled and carried, how they change through life, and how they are assessed.
Recovery3 min readPhysical recovery after training or injury
The phases of recovery, what the body needs for them, and when pain deserves an assessment.
Guides explain a health topic from the ground up. For articles on everyday health questions, see the Magazine
Guides by program
Closer looks at one subject each, grouped by the program they belong to.
The mitochondrial electron transport chain
How fuel becomes ATP3 min
The mitochondrial electron transport chain
How cells turn fuel into ATP, and where the chain loses efficiency.
Somatotrope physiology and pulsatile growth hormone dynamics
Pulses, muscle and fat3 min
Somatotrope physiology and pulsatile growth hormone dynamics
How the pituitary releases growth hormone in pulses, and what blunts them.
Muscle protein turnover and sarcopenia
Strength, protein and age3 min
Muscle protein turnover and sarcopenia
How muscle is built and lost day by day, why it matters for metabolism, and how to protect it.
Insulin sensitivity, fat storage and visceral adiposity
Where fat is stored, and why it matters3 min
Insulin sensitivity, fat storage and visceral adiposity
How the body stores fat, why its location matters, and what physicians measure.
Energy expenditure and fat oxidation
From store to fuel3 min
Energy expenditure and fat oxidation
How hormones tell the liver to burn stored fat, and what gets in the way.
Exercise physiology and metabolic adaptation
Movement and how the body responds3 min
Exercise physiology and metabolic adaptation
How working muscle takes up fuel, what regular activity changes, and what blunts the response.
Metabolic health: insulin sensitivity, appetite regulation and weight management
Hormones, not willpower alone3 min
Metabolic health: insulin sensitivity, appetite regulation and weight management
How hormones link the gut, the pancreas and the brain, and the blood markers physicians read.
Gut hormone biology and hypothalamic satiety signaling
How the gut talks to the brain3 minGut hormone biology and hypothalamic satiety signaling
How hormones from the gut tell the brain you have eaten, and what blunts the signal.
Gut hormone physiology and glycemic control
Gut, pancreas, liver and brain3 minGut hormone physiology and glycemic control
How the body steadies blood sugar after eating, and what makes that harder.
The science of telomeres: cellular aging and healthspan
Why cells stop dividing3 min
The science of telomeres: cellular aging and healthspan
What telomeres are, how their shortening ages cells, and how physicians assess cellular health.
Cellular stress resistance and repair: proteostasis and autophagy
Everyday wear and upkeep3 min
Cellular stress resistance and repair: proteostasis and autophagy
The maintenance systems that keep cells working, and why they fall behind with age.
Growth hormone signaling and visceral metabolic health
Hormones and deep abdominal fat3 min
Growth hormone signaling and visceral metabolic health
How growth hormone signaling relates to deep abdominal fat, and what physicians measure.
Neuroimmune signaling: the brain and the immune system
Illness, inflammation and thinking3 min
Neuroimmune signaling: the brain and the immune system
How the immune system and the brain signal to each other, and why inflammation affects thinking.
Adult neurogenesis and hippocampal plasticity
New cells in the adult brain3 min
Adult neurogenesis and hippocampal plasticity
Where new neurons arise in the adult brain, what supports them, and what suppresses them.
Neuroplasticity, synaptic integrity and cognitive healthspan
Plasticity, blood flow and signaling3 min
Neuroplasticity, synaptic integrity and cognitive healthspan
The mechanisms that support cognitive performance, and the risk factors in decline.
The stress response, anxiety and cognitive function
The stress response and the mind3 min
The stress response, anxiety and cognitive function
How the stress response works, why it sharpens and then impairs thinking, and what keeps it switched on.
Attention and memory: encoding, consolidation and retrieval
How the mind takes things in3 min
Attention and memory: encoding, consolidation and retrieval
How memories are formed, kept and recalled, and the common, treatable causes of poor memory.
Neuroprotection: how the brain defends its cells
The brain’s built-in defenses3 min
Neuroprotection: how the brain defends its cells
The barrier, antioxidants, support cells and sleep that protect neurons, and what weakens them.
Skeletal muscle hypertrophy and strength adaptation
How training changes muscle3 min
Skeletal muscle hypertrophy and strength adaptation
How muscle responds to load, what the adaptation depends on, and what holds it back.
Melanin biology, UV exposure and hyperpigmentation
Melanin, sunlight and dark patches3 min
Melanin biology, UV exposure and hyperpigmentation
How skin makes and distributes pigment, and why sun, hormones and inflammation leave dark patches.
Skin structure and nutritional physiology
Layers, blood supply and food3 min
Skin structure and nutritional physiology
The layers of the skin, how they are fed from the blood, and the nutrients they are built from.
Skin tone and radiance: the physiology of light reflection
Evenness, texture and light3 min
Skin tone and radiance: the physiology of light reflection
What makes skin look even and luminous, and the everyday factors that dull it.
Epidermal barrier function and transepidermal water loss
The skin’s outermost layer3 min
Epidermal barrier function and transepidermal water loss
How the outer layer of the skin keeps water in and irritants out, and what puts it under strain.
Dermal fibroblast activation and skin renewal
How skin makes and clears its matrix3 min
Dermal fibroblast activation and skin renewal
How fibroblasts make and clear the skin’s structural proteins, and what speeds their breakdown.
Dermal remodeling and extracellular matrix integrity
How the dermis is built and broken down3 min
Dermal remodeling and extracellular matrix integrity
How collagen is made and lost in the dermis, and what accelerates skin aging.
Vascular function and sexual response
Circulation and arousal3 min
Vascular function and sexual response
Why arousal depends on healthy blood vessels, and what a change in sexual function can signal.
The neurobiology of bonding, touch and closeness
How the body responds to closeness3 min
The neurobiology of bonding, touch and closeness
How gentle touch is sensed, how it calms the stress response, and what gets in the way of closeness.
The neurobiology of sexual desire
Where interest in sex begins3 min
The neurobiology of sexual desire
How the brain balances signals for and against desire, and the common reasons it falls.
Testosterone physiology in men
What the hormone does3 min
Testosterone physiology in men
How testosterone is made, carried and regulated, what it does, and what lowers it.
Male hypogonadism: symptoms, causes and laboratory evaluation
Signs, overlaps and blood tests3 min
Male hypogonadism: symptoms, causes and laboratory evaluation
How low testosterone is recognized and confirmed, and the reversible causes physicians look for first.
Hair fiber structure and keratin biology
What a strand is made of3 min
Hair fiber structure and keratin biology
How a hair is built in the follicle, what gives it strength, and what weakens it.
Scalp health: barrier, microbiome and the follicle environment
The skin your hair grows from3 min
Scalp health: barrier, microbiome and the follicle environment
How the scalp’s barrier, oils and microbes stay in balance, and what happens when they do not.
The hair growth cycle: anagen, catagen and telogen
Growing, resting and shedding3 min
The hair growth cycle: anagen, catagen and telogen
The phases every follicle passes through, and what pushes hair into shedding or thinning.
Immune homeostasis: regulation and tolerance
Responding without overreacting3 min
Immune homeostasis: regulation and tolerance
How the immune system restrains itself, and what happens when regulation fails.
Cytoprotective signaling and epithelial integrity
How the body’s linings protect themselves3 min
Cytoprotective signaling and epithelial integrity
How the gut lining protects and repairs itself, and what degrades it.
Neuropathic pain: how nerves signal and misfire
When the signal itself is faulty3 min
Neuropathic pain: how nerves signal and misfire
Why damaged nerves produce pain, how the signal is amplified, and the causes physicians look for.
Inflammation: acute response and chronic burden
Useful in bursts, costly when constant3 min
Inflammation: acute response and chronic burden
How inflammation starts and ends, and why the low-grade, lasting kind matters.
Cellular healing, tissue repair and gastrointestinal integrity
Repair, from blood supply to gut lining3 min
Cellular healing, tissue repair and gastrointestinal integrity
How tissue repairs itself and the gut lining stays intact, and what impairs healing.
Immunosenescence: how immunity changes with age
How defenses change over time3 min
Immunosenescence: how immunity changes with age
Why immune responses slow with age while inflammation rises, and what makes the change faster.
Tendon and ligament repair: collagen, load and remodeling
Slow tissue, steady loading3 min
Tendon and ligament repair: collagen, load and remodeling
Why tendons and ligaments heal slowly, the phases of repair, and why graded loading matters.
Cell migration and microvascular tissue perfusion
Cell movement and blood supply3 min
Cell migration and microvascular tissue perfusion
How injured muscle and tendon rebuild, and what impairs healing.
Cellular energy metabolism and its coenzymes
The coenzymes every cell runs on3 min
Cellular energy metabolism and its coenzymes
The coenzymes that carry energy in every cell, and what depletes the supply.
Brain energy metabolism and cognitive function
Why thinking takes fuel3 min
Brain energy metabolism and cognitive function
How the brain is supplied with fuel, why it is sensitive to any shortfall, and what strains the supply.
Cellular stress recovery: hormesis and adaptive responses
Strain, repair and rest3 min
Cellular stress recovery: hormesis and adaptive responses
How a manageable stress makes cells more robust, and why the benefit depends on recovery.
From nutrients to ATP: cellular respiration
From a meal to the cell3 min
From nutrients to ATP: cellular respiration
The steps that turn a meal into ATP, and the hormones, enzymes and vitamins each step needs.
B vitamins as metabolic cofactors
Small nutrients with a large job3 min
B vitamins as metabolic cofactors
What the B vitamins do in energy metabolism, who becomes deficient, and how deficiency is confirmed.
The hormones of fertility: how the reproductive hormones work together
What each hormone does3 min
The hormones of fertility: how the reproductive hormones work together
What FSH, LH, estradiol, progesterone and testosterone each do, and why timing matters in testing.
Neuroendocrine signaling: pituitary function, somatopause and metabolic recovery
How secretion changes with age3 min
Neuroendocrine signaling: pituitary function, somatopause and metabolic recovery
How growth hormone is released, how it falls with age, and the markers physicians read.
Ghrelin signaling and pituitary balance
One gland, several hormone axes3 min
Ghrelin signaling and pituitary balance
How the pituitary releases growth hormone in bursts without disturbing its other hormones.
Sleep architecture: stages, deep sleep and overnight recovery
What happens through the night3 min
Sleep architecture: stages, deep sleep and overnight recovery
How a night of sleep is structured, what deep sleep does, and what reduces it.
Neuroendocrine axis regulation: gonadotropic balance and reproductive healthspan
Hypothalamus, pituitary and gonads3 min
Neuroendocrine axis regulation: gonadotropic balance and reproductive healthspan
How the hypothalamus, pituitary and gonads signal to one another, and the markers physicians read.
Mitochondrial bioenergetics: metabolic signaling and cellular energy
How cells sense and make energy3 min
Mitochondrial bioenergetics: metabolic signaling and cellular energy
How mitochondria sense and make energy, and the markers of poor function.