Infrared sauna and weight loss: what's real
By the Find My Sauna team·
Updated ·
7 min read
Burn hundreds of calories, up to 600 a session, while you sit and relax. Some version of that promise turns up on infrared studio menus and home cabin websites. It sounds precise and scientific. It isn't, and the story of where the number comes from explains why.
The short answer
An infrared sauna won't burn fat in any meaningful way. The big calorie figures go back at least to a 1981 letter in a medical journal, which worked out the energy needed to evaporate sweat. That isn't the same as calories your body burns, and another doctor called the claim "highly doubtful" within months. Your heart does work harder in the heat, but the kilo or so you can lose in a session is water, and it comes back when you drink. Infrared can still support weight loss indirectly, by making recovery and a regular routine easier.
This guide looks at the infrared-specific claims. For saunas and weight in general, read does a sauna help you lose weight?
The claims you will see
Infrared marketing tends to repeat a few ideas:
- a session burns somewhere between 300 and 600 calories
- sitting in the cabin is like a workout without moving
- infrared melts fat, or lets you sweat out fat and toxins
- infrared heats you from the inside, so it works better than a normal sauna
The last one is easy to deal with. Far infrared is absorbed in the outer layer of your skin, and the heat reaches the rest of you through your blood, the same as in any hot room. The calorie numbers take longer to unpick.
Where the numbers come from
The oldest source we could find for these numbers is a 1981 letter to the Journal of the American Medical Association from a US Army doctor, Ward Dean. He wrote that sweating off 500 g in a sauna uses nearly 300 kilocalories, and suggested regular sauna use could rival exercise for conditioning the heart.
It was a letter, not a study. Early in 1982, another doctor, A. J. Searle, replied in the same journal calling the claim "highly doubtful". His argument was simple: people in hot climates sweat several litres a day, and if every half-litre burned 300 calories, they'd need to eat far more than people in cooler places, which, he pointed out, isn't the case. He also doubted that sitting still could train the heart the way exercise does.
Double the sweat and the same sum gives about 580 kilocalories, close to the 600 you now see quoted.
Why the sum does not add up
The 300 comes from physics. Turning water into vapour takes energy, about 0.58 kilocalories for every gram. Multiply that by 500 g of sweat and you get roughly 290. The problems:
- The heat mostly comes from the sauna. In a hot cabin, heat flows into your body from the heaters and the air. Sweating gets rid of it. The energy that evaporates your sweat is largely the sauna's electricity, not your fat.
- Not all sweat evaporates. Much of it drips off or soaks into your towel, carrying no heat away at all.
- Your metabolism is what burns calories. That does rise a little in the heat, because your heart is working harder, but it's a small increase on top of sitting still.
What actually happens in the cabin
A small study from Cardiff Metropolitan University, shared online by the maker of the cabin it used, gives a good picture of a hot session. Twelve healthy adults sat for 45 minutes in a far-infrared cabin at about 65 °C (149 °F). Their heart rates rose from 74 to 153 beats a minute, and they lost about a kilo of body weight each, almost all of it sweat. The volume of their blood plasma shrank by about 12%, then was back close to normal 30 minutes later.
A heart rate of 150 sounds like a run, but it isn't doing the same job. In the heat, your heart speeds up mainly to push blood to your skin so you can cool down, not to fuel working muscles. And the kilo on the scales is water you need to put back.
What the research shows
We couldn't find a well-run trial showing that infrared sessions alone reduce body fat. The research on infrared saunas is mostly small and short, and it has looked at relaxation, recovery after exercise and, in Japan, supervised heat therapy for heart patients.
Meanwhile the strongest evidence for any sauna, from long-term Finnish studies, is about heart health, not weight. More on what infrared is good for in infrared sauna benefits, and on the "sweat out toxins" idea in sauna detox.
Where infrared can help
An infrared session isn't a fat burner, but it can make the things that work easier to keep doing:
- Recovery. In a small 2015 Finnish study, 30 minutes in a far-infrared sauna seemed to help men recover from an endurance workout. Feeling less beaten up makes the next session more likely.
- A routine you enjoy. A booked sauna after the gym is a reward that keeps some people going.
- Winding down. Stress and short sleep make eating well harder. Half an hour of quiet heat helps many people relax.
Weigh yourself on a normal morning, not straight after a session, and don't judge progress by the post-sauna number.
Who should be careful
Never use a sauna to sweat off weight in a hurry, for example before a weigh-in. Losing a lot of fluid fast can cause dizziness, cramps and heat exhaustion. Drink before and after, don't go in hungry or after drinking alcohol, and talk to a doctor first if you are pregnant, have a heart condition, diabetes or kidney disease, or take medicine that affects blood pressure or fluid balance, such as diuretics.
This guide is general information, not medical advice.
Where to try an infrared sauna
Find My Sauna lists 699 places with an infrared sauna. These cities have the most:
Clear Mind Studio Fremantle
Perth · Private infrared suites
Sona Rooms
Melbourne · Infrared and contrast
Real Deal Wellness
San Diego · Private infrared rooms
Frequently asked questions
How many calories does an infrared sauna burn?
A little more than sitting still, because your heart works harder. Claims of 300–600 calories come from a sum about evaporating sweat, not from measuring what your body burns.
Does an infrared sauna burn fat?
No, not in any meaningful amount. Your body cools itself by sweating, not by burning fat.
Why do I weigh less after an infrared sauna?
You have lost water as sweat, often half a kilo to a kilo. It comes back as soon as you drink.
Is infrared better than a normal sauna for weight loss?
No. Neither is a weight-loss tool. Infrared is milder, so some people find it easier to fit into a routine.
Does sweating in an infrared sauna remove toxins?
Sweat is almost all water and salt. Your liver and kidneys do the clearing, and sweating adds very little.
