Is a Sauna Good for Weight Loss?

The honest answer: a sauna is not a weight-loss tool. You’ll step off the scales lighter after a session, but that’s water you’ve sweated out, and it comes straight back the moment you rehydrate. For actual fat loss, a sauna does very little on its own.

That’s not the answer the marketing gives you, which is exactly why it’s worth spelling out. Below we go through what the scales are really showing, how many calories a session burns, whether heat “boosts your metabolism,” and the ways a sauna can genuinely support a weight-management effort, indirectly and modestly.

Why the scales drop after a session

Sweat is roughly 99% water and electrolytes. A hot sauna session can produce anywhere from a few hundred millilitres to over a litre of sweat, which shows up immediately as lost weight, often half a kilo to a kilo or more. It feels dramatic. It’s also entirely temporary: your body defends its fluid balance tightly, and once you drink and eat normally the weight returns within hours. Nothing about your body fat has changed.

This is the single most misunderstood thing about saunas and weight. The number on the scale went down; the amount of fat on your body did not.

How many calories does a sauna actually burn?

A sauna session does raise your heart rate and your metabolic rate slightly, because your body works to cool itself. But the effect is small. Realistic estimates put a typical session at roughly 100–200 calories, about the same as a 20-minute walk. You’ll see far bigger numbers quoted online; treat those as marketing, not measurement.

For context, losing a single pound of fat requires a deficit of roughly 3,500 calories. Even taken at face value, a daily sauna session would take the better part of three weeks to account for one pound, and that’s before your appetite quietly makes up the difference, which it usually does.

Does heat “boost your metabolism”?

There is a short-lived rise in metabolic rate during and just after heat exposure, and there’s early, mostly mechanistic work on heat shock proteins and how repeated heat stress affects the body. But the leap from “metabolic rate rises briefly” to “saunas help you lose weight” isn’t supported. A 2018 systematic review of sauna bathing, published in Evidence-Based Complementary and Alternative Medicine, found reasonable evidence for cardiovascular and some other effects, but weight loss is not among the outcomes the evidence supports. The metabolic bump is real; it’s just too small and too brief to matter for body composition.

The infrared “burns 600 calories” claim

Infrared sauna marketing often quotes eye-watering calorie figures: 400, 600, sometimes more per session. These trace back to a single small, industry-associated estimate that has never been reproduced in independent research. An infrared cabin runs cooler than a traditional sauna and warms you directly, but there’s no good evidence it burns dramatically more calories, and certainly not enough to drive fat loss. If a claim about calorie burn sounds too good to be true, it usually is. Our infrared saunas guide takes an honest look at what infrared does and doesn’t do.

Where a sauna genuinely helps

None of this means a sauna is useless if you’re trying to lose weight. It just helps indirectly, as part of a healthier routine rather than as a fat-burning shortcut:

• Recovery. Easier recovery after training can mean more consistent exercise, and exercise is where the calorie deficit actually comes from.
• Sleep and stress. Regular sauna use is associated with better sleep and lower stress for many people, both of which support the appetite regulation and adherence that real weight loss depends on.
• Cardiovascular fitness. The heat load places a mild, exercise-like demand on your heart. It’s not a substitute for exercise, but it complements it.
• Habit and ritual. A sauna habit can anchor a broader wellbeing routine, and routines are what carry weight management over months.

In other words: the sauna supports the lifestyle that leads to weight loss. It doesn’t do the losing for you.

Sauna suits and “weight cutting”

You may have seen boxers or wrestlers using saunas or sauna suits to “make weight” before a weigh-in. That works, but only because it strips out water, fast, and temporarily. It’s a short-term dehydration tactic for hitting a number on a specific day, not fat loss, and it carries real risks if taken too far. It is not a template for anyone trying to lose weight healthily.

A word on safety

Because the “weight” you lose is fluid, the main risk of chasing it is dehydration. Drink water before and after every session, don’t use a sauna to deliberately shed water, and never combine it with crash dieting or alcohol. If you feel dizzy, sick or headachy, get out and cool down. Those are the early signs of heat exhaustion the NHS lists. For safe, sustainable weight loss, the NHS healthy-weight guidance (diet and physical activity) is where the real results come from.

Frequently asked questions

How many calories does a sauna burn?

Roughly 100–200 calories for a typical session, similar to a 20-minute walk. Much higher figures you’ll see quoted are marketing rather than measured. It’s far too small to drive meaningful fat loss on its own.

Can you lose belly fat in a sauna?

No. You can’t target fat loss from a specific area, and a sauna doesn’t burn fat in any meaningful amount anyway. Any drop on the scales after a session is water weight that returns when you rehydrate.

Do infrared saunas burn more calories than traditional ones?

There’s no good independent evidence that they do. The high calorie claims in infrared marketing come from a single unreplicated estimate. Both types burn a modest number of calories; neither is a weight-loss tool.

Is water weight real weight loss?

No. Losing water lowers the number on the scale temporarily, but it isn’t fat loss and it reverses as soon as you drink and eat normally. Real weight loss means losing body fat, which requires a sustained calorie deficit.

How long should you sit in a sauna to lose weight?

There isn’t a duration that turns a sauna into a weight-loss tool. The premise is the problem, not the timing. Staying longer just means losing more water and risking dehydration. For how long to use a sauna for its genuine benefits, see our guide to how long you should stay in a sauna.

The bottom line

A sauna is one of the better-evidenced wellness habits going, but weight loss isn’t one of the things it delivers. The scales drop because you’ve lost water, not fat, and it comes back. Where a sauna helps is around the edges: recovery, sleep, stress and cardiovascular fitness, all of which support the diet and exercise that actually move the needle. Enjoy it for what it does well, and don’t buy one expecting it to shift the scales.

If the health benefits are what interest you, our guide to what the sauna evidence actually supports is the place to start, along with the rest of our health & wellbeing guides. And when you’re ready to bring one home, you can find a vetted UK sauna builder near you.

Reviewed by the SaunaCentral editorial team. This article is educational and not a substitute for medical advice. Speak to your GP before making significant changes to your diet, exercise or heat exposure, especially if you have a health condition.