Does an infrared sauna burn calories or help you lose weight?
The claim that a session torches 600 calories traces back to a single old letter about boxers. What you actually lose on the scale is water, and it comes back with your next glass of it.
No, not in any way that matters for weight loss. The pound or two you see on the scale after a sauna is water you sweated out, and it comes straight back the moment you rehydrate, which you must.
A sauna does burn a small number of extra calories, because heating your body and running your heart faster costs some energy. But it is nowhere near the numbers on the studio wall, and it does nothing to your fat.
The sauna is genuinely worth using. Weight loss is simply not one of the honest reasons.
Where did the calorie claim come from?
A single old source, stretched for decades.
The widely repeated claim that a sauna session burns around 600 calories traces back to a letter published in JAMA in the 1980s, referencing energy expenditure in the context of athletes like boxers cutting weight. It was never a solid, general finding, and it has been passed around ever since, detached from its origin.
The reality, from what measurement exists, is that a typical sauna session raises your energy expenditure modestly, on the order of what a slow walk might add, not a hard workout. Your heart rate rises and your body works to cool itself, and that costs some calories, but a small amount.
Any studio quoting you a big round calorie number is repeating marketing, not measuring you. Our sauna detox guide covers a neighbouring myth that runs on the same wishful thinking.
Why does the scale drop then?
Because you literally poured water out of yourself.
In a hot session you can sweat out a pint or more of fluid, and a pint of water weighs about a pound. That is the entire explanation for the post-sauna scale drop. It is not fat, it is not permanent, and it is not a good thing to chase.
The instant you drink to rehydrate, which you should, that weight returns, because your body needs that water to function. Deliberately staying dehydrated to keep the number down is how you get dizzy, cramp, and unwell.
Fighters and wrestlers use this water-cutting trick to make a weight class temporarily, then rehydrate fast. It has nothing to do with fat loss and everything to do with a scale reading.
Does an infrared sauna change this?
No. The heat is gentler, and the physics are the same.
Infrared saunas run at a lower air temperature than traditional ones, so if anything they make you work slightly less hard. The marketing sometimes claims infrared uniquely mobilises fat or detoxifies it away, but there is no good evidence for that. Our infrared versus traditional guide covers the real differences.
You still sweat, you still lose water, and you still burn only a modest number of extra calories. Swapping traditional heat for infrared does not unlock a weight-loss mechanism that the other does not have.
The “infrared melts fat” claim is one to be actively skeptical of.
Does cold do any better for weight?
A little more interesting, but still not a weight-loss tool.
Cold exposure activates brown fat and slightly raises energy expenditure, which is a genuine physiological effect and more mechanistically real than the sauna calorie story. But when it has been studied for actual weight loss, the effect is small and inconsistent, and nobody has shown it meaningfully changes body weight. Our cold and metabolism guide covers exactly how far that evidence goes.
So neither heat nor cold is a weight-loss shortcut. Both are marketed as one because it sells.
So why use a sauna at all?
Because the real benefits are better than the fake one.
Regular sauna use has the strongest evidence in this whole field, and it is cardiovascular: large Finnish cohort studies link frequent use to lower rates of heart disease and death. Our sauna and heart guide covers the strength and limits of that data.
It also relaxes you, eases muscle tension, and, timed right, helps you sleep. Those are honest, worthwhile reasons that do not need a fabricated calorie count propped up beside them.
If weight loss is your goal, the levers are diet, strength training, and general activity, none of which a sauna replaces. It can be a pleasant part of a healthy life, not the engine of one.
The bottom line
A sauna burns only a modest number of extra calories, the 600 figure is a decades-old stretch, and the scale drop is water that returns the moment you rehydrate. An infrared sauna does not change this.
Use a sauna for your heart, your stress, and your sleep. For weight, look to the things that actually move it.
To find a sauna near you, start with our city wellness maps.