Does Sauna Actually Burn Calories?
Yes, but likely not as many as you’ve heard.
When you’re sitting in a sauna, your heart rate increases, your body sweats to cool itself down, and your metabolism rises a bit. A 2019 study in the Journal of Human Kinetics found that a 10-minute sauna at 100°C raised metabolic rate, but only about as much as a slow walk.
Claims that you can burn 600 calories in 30 minutes during a sauna session are misleading; they primarily refer to water loss, not fat loss. After a sauna, any observed decrease in body weight is due to fluid loss through sweating. Once you rehydrate, the weight returns. This temporary reduction is not true weight loss, but rather a result of dehydration during the session.
Realistically, a 20-30 minute sauna session will cause you to burn roughly 50 to 100 calories more than your resting metabolic rate. While this additional calorie expenditure can be helpful, it is not comparable to the calorie burn achieved through exercise.
What Does the Research Say About Sauna and Weight Loss?
To be honest, it’s complicated. There aren’t many large-scale studies, and current research does not support sauna use as an effective method for long-term fat loss.
But what research shows is that sauna use has metabolic and heart health benefits, which can help with weight loss in an indirect way:
A 2018 review published in Evidence-Based Complementary and Alternative Medicine found that infrared sauna therapy showed promise for people with type 2 diabetes and metabolic syndrome, improving glucose metabolism and reducing waist circumference in some participants.
Regular sauna use has been linked to improved cardiovascular function. A landmark Finnish study following over 2,300 men for 20 years found that frequent sauna bathers (4-7 sessions per week) had significantly lower rates of cardiovascular disease. Better heart health means better exercise capacity, which supports weight management.
There’s also emerging research on the relationship between heat therapy and mitochondrial function. Heat stress appears to trigger heat shock proteins and may improve how efficiently your cells produce energy — though this research is still in its early days.
The takeaway: a sauna isn’t a weight-loss tool on its own, but it may support systems that help you lose weight more effectively.
Is Infrared Sauna Better for Weight Loss Than Traditional?
This is where marketing claims start to pile up.
Infrared sauna companies often say their saunas are better for weight loss because they heat you from the inside and make you sweat more at lower temperatures. Some of these claims are true, but others go beyond what science supports.
Traditional Finnish saunas heat the air to 80-100°C, which then heats your body. Infrared saunas use infrared light to heat your body directly, even at lower ambient temperatures (typically 45-65°C). Both make you sweat. Both increase heart rate. Both have health benefits.
The 2018 study I mentioned earlier specifically used infrared saunas and showed positive metabolic effects. According to a study by Binghamton University in New York, raising your core body temperature in a sauna can reduce body fat. However, there’s still no strong evidence showing that infrared saunas are significantly more effective for weight loss than traditional saunas, so the best option is whichever sauna you will use consistently.
We sell both at Sisu. If you’re specifically interested in the metabolic benefits and prefer lower temperatures, infrared is worth considering. If you want the full Finnish experience — high heat, steam, the ritual of löyly — go traditional. Either way, the sauna isn’t doing the heavy lifting when it comes to weight loss. You are.
Can Sauna Help with Water Weight vs Fat Loss?
Let’s be clear about what really happens when you weigh yourself after a sauna session.
You will weigh less. That weight is water. Depending on the session length and your hydration levels going in, you might lose between 0.5kg and 2kg of fluid. This is why wrestlers, boxers, and other weight-class athletes use saunas before weigh-ins — it’s a reliable way to drop water weight quickly.
But this isn’t fat loss, and it doesn’t last. Your body needs that fluid replaced. If you don’t rehydrate, you’re just dehydrating yourself, which is bad for your kidneys, your performance, and your overall health.
That said, if you retain water — whether from a high-sodium diet, hormonal fluctuations, or frequent air travel — regular sauna use can help your body regulate fluid levels more efficiently over time. It’s not a dramatic effect, but it’s real.
Fat loss happens elsewhere: in a sustained calorie deficit, in building muscle that raises your resting metabolism, in sleeping properly, and in managing stress (which, incidentally, saunas help with).
What Role Does Sauna Play in a Weight Loss Routine?
This is where I can share my own experience.
When I was 130kg with chronic arthritis and eczema that dermatologists had given up on, I did a 40-day professionally supervised sauna detox program. According to one study, sauna use had positive effects on the locomotor system and alleviated arthritis-related pain. Within a year, I lost 42kg.
But was it just the sauna? According to research, overweight and obese individuals tend to experience the greatest body mass loss during sauna sessions, suggesting the sauna likely contributed, though other factors may have played a role. Absolutely not.
The sauna was just one part of a bigger lifestyle change. I changed my diet, became more active, focused on sleep, and managed stress better. Sauna became a daily habit that supported all these changes.
Here’s what it actually did for my weight loss:
Recovery: After exercise, the sauna helped my muscles recover faster. This meant I could train more consistently without the joint pain that had plagued me for years.
Sleep: Evening sauna sessions dramatically improved my sleep quality. Better sleep means better hormone regulation, lower cortisol levels, and fewer cravings.
Stress reduction: Spending twenty minutes in the sauna each day helped me reset. With less stress, I ate less for comfort and made better choices.
Ritual: Making sauna a daily habit gave me momentum. It became a key routine that made other healthy choices easier.
Over about 18 months, I lost 42kg, with daily sauna sessions contributing to the process, alongside substantial changes in my diet, physical activity, sleep, and stress management. Therefore, it is important to acknowledge that multiple lifestyle modifications may have influenced my weight-loss results. According to a study published in 2014, overweight and obese individuals can experience significant body mass loss during sauna sessions, highlighting its potential impact as part of a weight loss plan. However, these findings should be interpreted in the context of other concurrent behavioural changes that may also contribute to outcomes.
What’s the Catch? (The Honest Part)
If you buy a sauna thinking it will burn fat while you do nothing else, you’ll end up disappointed and out of money.
Here’s what sauna won’t do:
- It won’t create a calorie deficit for you
- It won’t build muscle
- It won’t fix a poor diet
- It won’t replace cardiovascular exercise
- It won’t work if you use it once a week
Sauna helps boost the effects of the other healthy things you do. But if you’re not doing those things, there’s nothing for it to help.
Some customers have told me they bought a sauna, used it a few times, and wondered why they didn’t lose weight. That’s like buying running shoes and expecting to get fit without using them.
Should You Buy a Sauna for Weight Loss?
If weight loss is your only reason for considering a sauna, I’d honestly tell you to spend that money on a gym membership or a home gym, a good personal trainer, or a dietitian first. Those will have a more direct impact on your weight.
But if you’re already working out, eating well, and want something to support recovery, sleep, stress management, and maintaining your healthy habits, then a sauna is worth considering.
The weight loss benefits are real, but they’re indirect. You won’t sweat off 10kg, but you’ll build habits that help you do better in all areas of your health.
That’s what happened for me. The sauna didn’t make me lose 42kg—it helped me become the kind of person who could.
Who is the Author?
Co-Author: Pat, Co-owner, Design & Construction
Pat is Finnish, and he has been building saunas most of his life. He grew up in a culture where sauna isn’t a luxury — it’s as essential as a bathroom.
Pat (Co-owner of Sisu) oversees design and construction of all Sisu’s custom-built saunas, bringing authentic Finnish techniques and an uncompromising eye for quality to every project. When it comes to timber selection, heater placement, or ventilation design, he’s the authority.
