Humans have been adapting to stress throughout evolution.
Two common stressors in human history have been going long stretches of time without food (fasting), and heat stress.
Fasting is an ancient health and longevity practice that has been used by various cultures and religions for millennia.
It’s not about starving yourself to lose weight. Fasting is proven to improve brain, physical, and spiritual health.
While saunas have also been around for thousands of years, the practice of becoming heat acclimated to survive high temperatures is part of our evolution.
Today, people are using a combination of the two because of the robust effects on the body.
Using the sauna in a fasted state can be a potent fat burning, body healing, brain-boosting, and anti-aging strategy.
While this is a regular strategy of mine, it is not for everyone.
Benefits of fasting
Fasting is the abstinence of food, or any calories, for an extended period of time. You are not fasting if you consume 1 calorie.
Fasting improves body composition by switching to burning fat, instead of glucose. This improves blood pressure, blood sugar, and insulin sensitivity.
It also increases the body’s secretion of human growth hormone. Growth hormone are critical to metabolism, repair, and growth of new tissue, which helps in burning fat and maintaining muscle.
Fasting also improves a number of biochemical processes that optimize human performance, longevity, and immunity.
Fasting induces cellular autophagy; the process in which cells in our body degrade damaged components within the cell. Autophagy means self-eating.
This helps clean up harmful material inside cells and repairs them. The recycling of damaged cells can prevent diseases.
Improved brain function
Autophagy also happens in your neurons, thus protecting nerve cells.
On top of that, the brain hormone BDNF increases, which aids in growing new nerve cells, and improving memory and learning.
Types of fasting
A fast may be done for various purposes, spiritual, gut repair, autophagy, etc.
The term “fasting” is a broad one, comprising multiple types and subtypes of the practice, including intermittent and multiple-day fasts.
These fasts can range in duration and degree of restrictiveness.
Intermittent fasting (IF) has become popular in recent years. This has shined a brighter light on the already well-known beneficial effects fasting has your metabolism and lifespan.
Intermittent fasting is an eating pattern where you cycle between eating and fasting. It’s not about what foods you can and cannot eat. It’s about when you can eat.
Intermittent fasting is often interchangeable with time-restricted feeding (TRE). There is definitely overlap between IF and TRE because both are a prolonged fast.
Time restricted eating refers to the consumption of calories only within a specific time window, say from 12 noon to 8pm. You are in a fasted state the rest of the day, not eating anything from 8:01pm-11:59am.
TRE does not reduce caloric intake within the feeding window.
Research has shown that limiting your feeding window to 8, 6, or 4 hours dramatically reduces inflammation, increases energy, burns fat while maintaining muscle mass, has a number of cognitive benefits, increased endurance, improved cellular repair, and much more.
IF can take several forms because it is a very broad term.
Common forms of Intermittent fasting
16/8 method: Discussed earlier, this is the most common form of IF and the best method for beginners. This involves fasting for 14-16 hours and restricting your feeding window to 8-10 hours.
The simplest way is to skip breakfast and eat from 12-8pm.
An amazing book on the practice of eating two meals a day comes from health & fitness author and athlete, Mark Sisson:
One meal a day: This is often referred to as The Warrior Diet. You essentially don’t eat all day until the early evening.
This is the logical next step for beginners, coming from 2 meals a day with the 16/8 method.
Jack Dorsey and Lex Fridman (among others) have made this popular:
Alternate Day Fasting: Some people do alternate day fasts, where they eat normally one day, then fast the next.
Fasting mimicking diet: Others will adopt a very low calorie diet for 2 days out of the week, while eating normally the rest. This is known as 5:2 fasting or the fasting-mimicking diet..
Prolonged Fast: Then there are prolonged fasts of over 24 hours. 3 and 5 day fasts have become popular amongst fasters.
Either way, consuming the exact same amount of food and calories within an 8 hour window is much better for your body compared to stretching that exact same food intake over 16-20 hours.
Additional resources on fasting
Dr. Satchin Panda is one of the leading experts on fasting and the circadian code. His book is a must read for your health.
This book from Dr. Jason Fung does a great job of diving into the different forms of fasting and their benefits:
Sauna while fasting
Your body’s response to heat stress leads to similar benefits as fasting; including cellular autophagy, growth hormone release, improved metabolic function, and brain performance.
Sauna use for longevity
Heat stress induces autophagy. It does this by activating heat shock and FOXO proteins.
Heat shock proteins (HSP) prevent protein disorder and aggregation by repairing damaged proteins.
Damaged proteins can clump together. These clumps are often found in cardiovascular, Alzheimer’s, Parkinson’s, and Huntington’s diseases.
Extreme temperatures (sauna) and fasting, both increase the expression of HSP’s to repair damaged proteins.
FOXO proteins play an important role in human lifespan and healthy aging. They regulate many genes that combat cellular aging; like damage to DNA, proteins, and lipids, and loss of stem cell function.
FOXO proteins increase the production of genes to regulate DNA repair, tumor suppression, stem cell function, immune function, and protein aggregation.
During heat stress, these FOXO proteins form with sirtuin 1. SIRT1 is an enzyme that also influences aging and longevity. It enhances FOXO’s resistance to oxidative stress, plus has its own influence on metabolic processes that promote longevity.
All of this combats the effects of aging.
A famous study of 2315 middle-aged men from Finland followed the men over 20 years to see how sauna use impacted their health and longevity. The findings were amazing.
The men who used the sauna 4-7 times per week were 50% less likely to die from cardiovascular-related diseases, and 40% less likely to die from all causes of premature death.
While fasting releases growth hormone production, saunas are even more powerful in doing so.
According to Dr. Dan Huberman of the Huberman Lab Podcast, the three lifestyle factors to increase human growth hormone are:
- Increase deep sleep
- Exercise (but not working until failure)
- Sauna at 176-210 F, for 20-30 minutes. This has been shown to have a 16 fold increase on human growth hormone 16 fold.
As mentioned previously, growth hormone release help the metabolism from tissue repair to maintaining cognitive function, and body composition.
Our body releases growth hormone when we don’t have enough calories but still need to maintain muscle.
Brain-boosting effects of sauna use
Then there are the brain boosting effects of sauna use. Being in a sauna increases brain-derived neurotrophic factor (BDNF).
BDNF is a protein that promotes the growth of new neurons. It is involved in muscle repair and regrowth in the body, and also with cognition.
Heat stress increases the production of BDNF to promote neurogenesis (the growth of new neurons in the brain). BDNF expression is active in the brain in areas involved in learning, long-term memory, and cognitive function.
The activation of BDNF from heat stress may have been a factor in why that large study of Finnish men who used the sauna 4-7 times per week were also 65% less likely of developing Alzheimer’s disease than those who used the sauna once per week.
Both sauna use and fasting increase BDNF, so the combination of the two amplifies the effects even more.
On top of the activation of BDNF, norepinephrine is also the released. Norepinephrine is a hormone and neurotransmitter in the brain. Increasing norepinephrine enhances focus and attention.
Then there is prolactin. Prolactin is a hormone released in the pituitary gland, which promotes myelin growth. Myelin growth makes the brain faster and repair nerve cell damage.
There is one study of men using a sauna at 176°F that showed their norepinephrine levels increase by 310% and prolactin levels increase by 900%.
A similar study of women in a 20-minute dry sauna say an 86% increase in norepinephrine and 510% increase in prolactin.
Combining fasting and saunas
Fasting and saunas both stress the body in good ways. They both help improve cognitive and metabolic function, while repairing the body. These two can be a potent strategy when used together.
In a recent podcast episode about biohacking your fast, Ben Greenfield says saunas are a way to enhance the benefits of a fast.
He sticks to largely aerobic exercises, sauna, walking, yoga, swimming, etc. instead of intense workouts, during a fast.
Ben combines his sauna sessions with cold thermogenesis via a cold plunge or cold shower. The cold upregulates fat enzyme conversion even more.
Combining fasting, with sauna, and cold leads to enhanced fat loss by up-regulating the conversion of white fat into brown fat.
When to use the sauna while fasting
There are 2 optimal times to use the sauna when fasting.
If you are doing 16/8 fast where you eat only between 12-8, the best time to use the sauna is mid-to-late morning.
For extended fasts or eating one meal-a-day, the best time to use the sauna in a fasted state is in the afternoon or evening, at peak body temperature. The sauna session and cold plunge would be done a couple of hours before you eat.
Obviously people have busy schedules so get the sauna session and cold plunge in whenever you can.
How to start fasting
I used to eat the moment I woke up until the moment I went to bed. It took me several months to be able to fast for an extended period of time.
What I did was slowly shrink my feeding window, by an hour at a time. So if I normally ate at 8am, I delayed it until 9, then 10.
It took me a few weeks or months to get to the point where I wasn’t eating until at least 12 noon. Now, I almost never eat in the morning.
I was eventually able to extend my fast until 2, or 3 in the afternoon. Then, I could go a whole day without eating until dinner.
I’ve done several 24+ hour fasts now.
You don’t get any hungrier. Your energy levels are higher and you have better focus when fasting, contrary to popular opinion.
It’s also much less of a burden to always worry about when you are going to eat. If meetings run long, I know I don’t need to eat. I can work through lunch, without skipping a beat, and just wait until dinner.
That’s metabolic flexibility.
This is the same advice that Dr. Dan Pompa gives in his book Beyond Fasting.
He recommends to squeeze your window so if you are normally eating 10 hours, eat 9 hours, then 8. Eventually you will get down to 4 hours, then be able to only eat one meal a day.
This leads to mitochondrial stress so your body gets used to burning fat.
Who should not use the sauna while fasting?
I am obviously no medical doctor so please use common sense and check with your doctor before trying.
You shouldn’t just jump into an extended fast if you are not already doing some form of fasting. You can try the strategy outlined above, and read from the books I recommended.
If you are not used to the sauna, you may want to start building your heat tolerance before trying to be in the sauna while fasting.
And if you have other medical conditions, consult your doctor before trying.