Lower risk of:

It also allows:

The Biology of Heat

How do we heat up?

  1. From the outside (the environment, the clothes, etc.)
  2. From the inside.

We have two types of body temperatures:

  1. Temperature of the skin (shell). The shell acts as a thermostat.
  2. Temperature of the core (organs, nervous system). Is always higher than the temperature at the surface.

The body and brain try to balance these temperatures in the appropriate way.

The body receives the temperature signals to release certain chemicals that will cool us down or heat us up.

Thermal Regulation

Thermoregulation is a process that allows your body to maintain its core internal temperature.

All thermoregulation mechanisms are designed to return your body to homeostasis. This is a state of equilibrium.

Unlike cooling down, heating up the body too much can be dangerous (hyperthermia).

Circuit: within the skin (shell) we have neurons that have receptors on them which sense changes in heat. When you get into a hot environment, your shell senses the heat and activates the neurons in the Pre-Optic Area (POA)

Neurons in the POA have the ability to send signals to get you to heat up and actually change your behavior. It changes how you think and feel.

The POA kicks off responses that are autonomic and subconscious and also kicks off behavioral responses (feeling lethargic, spreading limbs).

When we get in an environment very hot, the POA sends a signal to the amygdala, the brain area that activates the sympathetic Nervous System (fight or flight). The impulse of getting out of the sauna is due to this signal to the amygdala, which activates the release of adrenaline.

Sauna for Longevity

The use of deliberate heat exposure is powerful to increase health and longevity.

The more often that you do sauna, the better.

How many times a week?

2–3 times a week: 27% less likely to die of a cardiovascular event than people who did once a week.

4–7 a week: 50% less likely to die of a cardiovascular event than people who did once a week.

How to do Sauna

Temperature ranges: 80C (176F) — 100C (212F)

Duration: 15-20 minutes per session

Timing: Two hours before waking, body temperature is at its lowest (temperature minimum). The body temperature increases throughout the day and starts decreasing in the late afternoon to help the transition to sleep.

Heat exposure decreases core body temperature.

To optimize GH release and sleep: don’t eat two hours before sleep and do the sauna close to sleep and in a fasted state.

Hydration: You lose water in the sauna. You need to replace it. Drink 16 ounces of water for every 10 minutes of sauna.

Andrew’s Protocol: 3 20-minute sessions every week. After a workout or later in the evening.

Heat Exposure tools

Sauna is the most convenient way to do it. But you can induce heat in other ways:

Dry sauna vs wet sauna: it does not matter, do whichever you prefer.

Infrared saunas: they are not hot enough to get the health benefits.


When you get into a hot environment, your shell senses the heat and activates the neurons in the POA, which in turn activates mechanisms in the Autonomic Nervous System. Some physiological responses to sauna:

These responses look a lot like cardiovascular exercise. You are basically getting a cardio workout.

Hormone Effects of Sauna

Tool to reduce stress:

Study: Four sauna sessions of 12 minutes each, at 90°C. After that, they did a 6-minute cool water immersion or cold shower→ Results: Cortisol decreased.

Growth Hormone

GH is secreted from the pituitary. The signals arrive from the neurons in the hypothalamus.

GH impacts metabolism and growth and repair of cells.

At around 30 years old, the levels of GH release start to decrease.

How to get a 16x fold increase in GH

Study: Ten healthy male and seven female volunteers were exposed to dry heat (in a Finnish sauna at 80°C) for 1 h twice a day for 7 days.

GH in males exhibited 16-fold increases.

Don’t do it more than once a week because you are going to get heat adapted.

Heat Shock Proteins (HSP) and Metabolism

Beige and brown are rich in mitochondria and increase metabolism. Beige and brown fat help burn white fat.

Activation of HSP: a protective mechanism to rescue proteins that otherwise misfold.

HSP prevent the changes in proteins that would be detrimental to health.

Sauna exposure activates HSP.

FOXO3: Involved in DNA repair pathways. From the time we are born, there is a constant repair of our proteins and cells. It is involved in the clearing of senescent cells (zombie cells).

Sauna exposure up-regulates levels of FOXO3.

People born with FOXO3 are 2.7x likely to live more than 100 years.

57 minutes per week of heat exposure in conjunction with 11 minutes of cold exposure are the threshold for improving metabolism and brown fat.

Improvements in Mood and Mental Health

Sauna use can sensitize the receptors of the opioid system. It improves our capacity to feel good and experience pleasure in other situations.

Endorphins are released in response to stressors. The endorphin system is not just about feeling good, it’s also about feeling bad.

Dynorphins: they make us feel worse in response to stressors. When we get into a sauna dynorphins are released (discomfort we feel). Dynorphin binds to the kappa receptor. In consequence, the brain produces more mu-opioid receptors, sensitizing them to endorphin and future endorphin exposure.

Elevating the body temperature also has a very robust anti-depressant effect.

Local Hyperthermia & Local Heat Therapy

Glabrous Skin: palms of hands, the upper half of the face, and bottoms of the feet. These surfaces have specific types of veins that don’t have capillaries between them. So heat and cold can move very quickly from these areas and change our core body temperature.

Putting cold into these areas can be a life-saving technique if someone is suffering from hyperthermia.

Local heat therapy: Heating a particular surface of the body can convert the white fat to beige fat, which in turn increases metabolism.

Mechanism: Local heating of the skin converts a metabolically sluggish or inactive cell type (white fat cell) into the metabolically charging beige fat cell which leads to systemic increases in metabolism via two mechanisms: First, via increases in UCP1 (increases mitochondrial function). Second, via Increases in Heat shock factor 1 and a2b1 (lipid and glucose metabolism and regulation).

This doesn’t mean spot reduction of fat is possible with local heating of tissue.

Burning the skin leads to very large increases in metabolism and fat burn (DON’T BURN YOUR SKIN ON PURPOSE). Don’t put anything that damages your skin.

Protocol: Exposure of upper back at 41 degrees for 20 minutes. Three days per week.

Local hyperthermia therapy mimics deliberate cold exposure.

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