I know what you’re thinking: “maybe if I combine daily fasting, exercise five times per week, some cold baths, and even use a sauna while fasting, my fat loss efforts will skyrocket.” And, you’re certainly right, in the short term…
However, such extreme approaches can also backfire in the long run. For that reason, I decided to write a blog post about using a sauna while fasting so that potential side effects are minimised.
In this blog post, first I’ll talk about some fasting basics. Next up, I’ll give you five lessons to keep in mind when you're in a sauna fasted. Let’s start with the beginning though:
Fasting has become extremely popular in the last decade. Many different fasting protocols exist though, in the same way, many different training programs exist. Nevertheless, many people have been very successful in using fasting to reduce their body weight and fat mass and become healthier overall.
And, success leaves clues. For that reason, lots of science has been published on fasting as a health tool in the last few years (1; 2; 3; 4; 5; 6).
Even though fasting only has a slight benefit compared to regular dieting (i.e. “caloric restriction”), for many people it’s much easier to implement into their day.
For instance, you can follow a 16/8 “intermittent fasting” schedule. During such a schedule, you’re fasting 16 hours a day and eating during an 8-hour window. Another very popular approach is the “One Meal A Day” (OMAD) approach, where you’ll eat one big meal per day, usually in the evening. And to follow the 16/8 protocol, you'll basically only have to skip breakfast.
Of course, during your daily life, it takes people some time to get accustomed to not eating. During the fasting window, your body needs to learn to burn the carbohydrates that are still stored in your muscles and liver, and once these are burned off, to rely on your body fat.
Many people are used to eating every few hours when they’re awake. In that case, getting used to fasting and not consuming any calories for long periods of time can be difficult. Suffice it to say that fasting is a stressor on the human body.
Don’t be alarmed by the term “stress” though. Stress can be healthy for humans, assuming the stress isn’t excessive. In biology, that principle is called “hormesis” or “hormetic stress” - meaning that in small or medium-sized portions, the stress ensures that the organism becomes stronger (7; 8; 9).
Exercise is a hormetic stressor, for instance. If you exercise in controlled dosages, you’ll become healthier overall. Of course, there’s a limit to your ability to get stronger through exercise - if you don’t rest sufficiently, you’ll get weaker over time because the stress is too much for the organism to handle.
Fortunately, many people have extremely good results from fasting. Examples of such results are reversing their type-2 diabetes, improving their heart, blood vessel, and metabolic health, feeling a lot more healthy and energetic, and much more.
Some studies also conclude that fasting is superior to the old-fashioned calorie restriction in the first place.
In all cases though, you’ll still get the results if you manage the stress of fasting well. In the sections below, I’ll thus explain a bit more about managing the temporary stress fasting gives:
Lesson 1: You’ll Burn Even More Calories
Fasting increases the number of calories you’re burning because you’re not consuming any calories at that moment, and, your body needs to use its stored calories to generate energy.
And, even though it’s more of an advanced technique, using a sauna whilst fasting creates double the “hormetic” response I talked about before. In an earlier blog, I explained how many calories you burn during different sauna sessions. Per hour, studies show that you burn between 600-1,200 kilocalories (I’ll abbreviate that name as “calories” as it’s commonly used as such).
Those numbers are higher than running, walking, or playing golf, so your body is quite active. It’s very hard to add the calories you burn during fasting on top of those numbers though, as context matters a lot here.
For instance, if you’ve eaten a lot of carbohydrates the night before, then your liver and muscles might have stored those carbohydrates as “glycogen”. In that case, that glycogen is burned off first before your body fat stores are used.
However, if you ate a small or normal meal in the evening before, then most of those carbohydrates were probably burned during the day. So next up, during your sauna session, you’re burning even more calories from body fat than you’d do by fasting alone.
Let’s focus more on the topic of body fat though:
Lesson 2: You’ll Burn More Energy From Body Fat
So let’s continue the journey on what happens if you take a sauna whilst fasting. Let’s assume you’ve burned through most of the carbohydrates in your body while you’re sitting in a sauna. In that case, your body will start burning body fat directly to generate energy.
As a side note, I take a middle position between the “calories in, calories out” and the “avoid carbohydrates to burn body fat” positions that are hotly debated within the current science (10; 11; 12). Under both theories, you either have to limit the calories you’re eating or the carbohydrates you consume - on a daily basis.
And, under both circumstances, after you limit either calories or carbohydrates, the combination of saunas and fasting ensures that you lose body fat super fast. Of course, you can make this dynamic even more extreme by adding exercise in the mix, but, you’ll have to slowly build up your tolerance as you’re adding stress on top of stress.
Suffice it to say that you’ll become a fat-burning machine by sitting in a sauna fasted. Some of our internal studies also show that saunas are excellent for losing body fat, even without fasting.
Next up, let’s consider another important topic:
Lesson 3: You’ll Have To Be Careful Ingesting Enough Electrolytes
If you’re spending time in a sauna, you’re losing so-called “electrolytes”. Sodium and chloride, which together make up salt, are major examples of such electrolytes. Other examples are magnesium and potassium.
Now here’s the deal:
If you’re fasting, you’re not consuming any electrolytes for a time. And, at the same time, your need for electrolytes increases. Hence, it’s more likely that you become depleted of electrolytes during that time.
I’m not saying you should be scared - I’m just telling you to be a bit more careful, especially if you’re in poor health. Salt - consisting of sodium and chloride - is the most important electrolyte to replenish during and after sauna visits. You can simply add a teaspoon of natural salt to every litre of water to avoid becoming depleted.
And, if you want to do even better, make sure you get a high-quality potassium and magnesium supplement as well. Use that supplement during the time you’re fasting. If you don’t want to supplement, then smoothies with vegetables that are extremely low in calories - such as spinach and celery - are a great option too.
Effect 4: You’ll Have To Manage Blood Sugar Levels More Carefully Than If You Don’t Fast
Again, fasting during a sauna adds stress on top of stress. If you’re in poorer health, then combining both therapies will place greater demands on your body.
For instance, if you’re pre-diabetic - and therefore already have problems managing your blood sugar levels - then using a sauna while fasting might give you low blood sugar levels. Symptoms of low blood sugar levels include shakiness, an irregular heartbeat, potential fainting, sweating, headaches, nausea, the strong need to eat, and more.
This problem is really easy to prevent though. First up, if you’re in poor health or have a chronic health condition, consult with your physician first before combining fasting and saunas. Secondly, slowly build up your fasted sauna sessions over time so that your body gets used to the stress slowly over time and becomes stronger.
Effect 5: You Need To Be More Careful With Evening Sauna Sessions
First, I’ll make a short detour: Fasting, all by itself, raises your stress hormone levels. “Cortisol” and “adrenaline” are examples of these stress hormones. And, if you’re sitting inside a sauna fasted, those stress hormone levels will increase even more (13; 14; 15; 16; 17).
Stress hormones aren’t bad in and of themselves. Without stress hormones, your body cannot generate energy, for instance. But, chronically high levels of stress hormones are bad for your health.
And, improper timing of stress hormones is also problematic. I’ll help you understand with a simple analogy:
If you’re exercising right before bedtime, the adrenaline prevents you from going to sleep. But, if you exercise in the early evening or before that, your body can wind down again and you’ll sleep like a baby.
In the same way, fasted sauna sessions are better not used later in the evening. One problem fasting creates is that you probably need to break your fast later in the evening as well.
For instance, if you engage in a fasted sauna session at 6 PM, and get out of the sauna at 7, you’ll still have to eat.
Also, if you’ve been fasting all day, you probably also need to eat a big meal. As a result, you’ll be consuming a very big meal right before bedtime, impeding your sleep quality.
Normally, I recommend sauna sessions during the late afternoon or evening. That routine helps many people sleep much better once they cool down after a session. However, if you’re fasting all day, it’s better to plan your fasted sauna session earlier on the day.
That way, your stress hormones have time to come down again. Also, your body will have more time to process the meal, preventing you from going to sleep on a stomach that is too full.
So, fasted sauna sessions can be problematic in two ways if timed improperly: first, your stress hormone levels might become too high before bedtime. And secondly, meal timing can be thrown off if you use a sauna late in the evening.
Conclusion: Be Careful And Multiply Your Results
Like I stated in the introduction, you can combine many different stressors and get great results. Well, if you're 18 or 30 years old, that is. At that age, you can fast, alternate sauna sessions with cold therapy, drink coffee for even quicker fat loss, and then do a workout afterwards as well.
But, more is not always better. With age and if you've got health problems, you have to be more careful with saunas while water fasting. Dry fasting I never recommend under any circumstances, and, certainly never in combination with a sauna. As stated before, taking in electrolytes and some water is very important.
Hopefully, with these lessons, you're better able to understand how to plan to use a sauna while fasting. And, lastly, read my blog on building a daily sauna routine if you'd like even more understanding of this topic.