Can you actually increase your metabolism in an infrared sauna? How many calories do you really burn – and what happens in the body after 10, 20 or 30 minutes in infrared heat?
Interest in infrared saunas has increased sharply in recent years. Many people use saunas for relaxation, recovery, and stress reduction. At the same time, it is often claimed that infrared heat can contribute to increased metabolism and weight loss. This is largely true, but the underlying mechanisms are complex.
Two mechanisms: why infrared sauna can support weight loss
When talking about infrared sauna and weight loss, it's important to understand that there are several underlying mechanisms. Primarily, there are two main mechanisms.
1. Increased energy consumption
In an infrared sauna, the body absorbs infrared wavelengths that heat the tissue directly. This differs from traditional Finnish saunas, where the air is heated first.
When the body is heated by deep infrared radiation, several physiological processes occur simultaneously:
- blood vessels dilate
- circulation increases
- heart rate rises
- sweat glands activate
- body temperature increases
This activates the body's thermoregulatory system, which actively works to stabilize temperature. All these processes require energy, so the body's energy consumption increases during heat exposure, even when sitting still. In a sauna session, one can often achieve a so-called "fat-burning heart rate," i.e., 60-70% of a person's maximum heart rate, which is the optimal zone where the body burns fat.
Studies that have measured energy consumption during sauna show that heat exposure can increase the body's metabolism compared to rest. In a study published in BioMed Research International, the energy consumption during a 30-minute sauna session was estimated to be around 300–600 calories, depending on body weight, sauna temperature, individual physiological response, and how well acclimated to heat one is.
2. Reduction of environmental toxins in fat tissue
The other mechanism, and equally important, concerns how environmental toxins in the body can affect metabolism.
Several studies show that many chemical substances are stored in the body's fat tissue because they are often fat-soluble. These substances are often referred to as obesogens, because they can affect fat cells, hormone balance, and metabolism.
Research suggests that certain environmental toxins can:
- stimulate the development of new fat cells
- increase the volume of existing fat cells
- disrupt hormone balance
- block the body's natural fat burning
This can make it more difficult for the body to regulate weight.
When the body is heated through an infrared sauna, both circulation and sweat production increase. The heat directly affects fat cells to "release" environmental toxins and mobilize them. This occurs either through sweat or via our detoxification pathways: such as the kidneys, liver, lungs, etc. (urine, feces, breath).
Several studies have shown that sweat can contain various environmental toxins, including:
- heavy metals
- BPA
- certain pesticides
This does not mean that sauna alone detoxifies the body, but sweating can be one of several natural ways the body uses to eliminate waste products. In addition, the heat also stimulates the liver to detoxify "better and more efficiently" by increasing the body's antioxidant defense, which plays an important role in neutralizing toxins in the body. You can read more about this topic in the article Sweat – the body's detoxification system and in the article Environmental toxins and weight loss.
How the body reacts during an infrared sauna session
What happens in the body after 10 minutes in an infrared sauna?
The first few minutes in the sauna act as a warm-up phase.
Typical responses include:
- blood vessels dilate
- heart rate increases
- blood flow to the skin increases
- the body begins to sweat
This happens because the body tries to transport heat from the body's interior to the skin surface. At this point, energy consumption is still relatively moderate.
Detoxification begins in these initial 10 minutes.
What happens after 20 minutes?
After about 20 minutes, the body is in a more active thermoregulation phase.
Common physiological responses:
- heavier sweating
- increased heart rate
- higher circulation
- increased metabolic activity
The heart rate can increase to levels similar to light physical activity.
What happens after 30 minutes?
After about 30 minutes, the body's heat balance is more stable.
At this point, many experience:
- significant sweating
- increased energy consumption
- higher heart rate
- strong feeling of heat
It is also often at this point that a clear weight loss is observed on the scale after a sauna session. This is mainly due to fluid loss through sweat. But between 20-30 minutes, the body is at what is called moderate intensity exercise and can, in the long term, help support a better metabolism and fat burning.
How does an IR sauna affect our metabolic health?
During a session in an infrared sauna, several processes occur in the body that affect metabolism, hormones, and metabolic health.
When the body gets warm, it must actively work to cool itself down. The heart beats faster, blood vessels dilate, and blood circulation increases. This causes the body to use more energy – the heart rate can actually reach levels similar to light to moderate physical activity, leading to a temporary increase in metabolism.
Heat also triggers a positive stress response in the cells. The body produces, among other things, heat shock proteins, which help cells with maintenance and repair. At the same time, heat can stimulate signals related to mitochondria, the cell's small power plants, which play an important role in how the body produces and uses energy.
Sauna can also affect how the body handles blood sugar. Regular heat exposure can contribute to better insulin sensitivity, making it easier for the body to use glucose as energy instead of storing it.
Regarding hormones, the body's stress response is activated first when the temperature rises. Eventually – especially when sitting calmly in the heat – a reduction in the stress hormone cortisol is often observed, while the body shifts more into a relaxed, parasympathetic state. This can contribute to better recovery and lower perceived stress.
From the first drop of sweat, the body also begins to shed heat through perspiration. Sweat consists mainly of water and salts, but can also contain small amounts of environmental substances. Some of these substances are referred to as obesogens, because they can affect hormone balance and fat storage. Although the liver and kidneys still do most of the body's detoxification, sweating can help to excrete small amounts of such substances.
Can an infrared sauna replace exercise?
Sauna mimics some of the effects of physical exercise, but cannot completely replace it. Physical activity directly activates muscles and leads to a stronger metabolic response. Sauna, on the other hand, can contribute to a moderately increased energy consumption because the body uses energy to regulate temperature and maintain balance. Sauna is also a low-threshold option for many who, due to illness or other life stresses, are unable to exercise. Studies have shown that muscle wasting can be reduced by over 40% with sauna. This means that if you don't exercise but use a sauna, it can help maintain muscle mass that would otherwise not be the case. You can read more about this in this article.
Summary: Can an infrared sauna help with fat burning?
Research shows that infrared saunas can:
- increase energy consumption
- stimulate circulation
- activate the body's temperature regulation
- support the body's natural detoxification processes
- contribute to stress reduction and better sleep
- lower blood sugar
- lower inflammation
- improve metabolic health
However, it is important to understand the limitations. Lasting weight loss requires a holistic lifestyle with:
- balanced diet
- physical activity
- good sleep
- stress reduction
When used regularly as part of a holistic lifestyle, an infrared sauna can be a valuable tool for health, well-being, and metabolic support.
