Quick Definition
A sauna cut is the practice of sitting in a hot sauna to sweat off water weight in the days or hours before a fight, so an MMA fighter can reach a lower weight class at the official weigh-in and then rehydrate before stepping into the cage.
What is a sauna cut?
MMA fighters compete in weight classes, and most of them walk around heavier than the limit they fight at. To qualify, they shed pounds in the week before a bout. The sauna is one of the tools they use to do it. Heat makes the body sweat, sweat drains body water, and body water has weight, so a fighter who sweats out several pounds in a sauna reads lighter on the scale.
The important thing to understand is what kind of weight this is. A sauna cut removes water, not fat. That water comes back the moment a fighter starts drinking and eating again, which is exactly the point. A fighter makes weight at the weigh-in, then rehydrates and refuels before the fight, often stepping into the cage 10 to 20 pounds heavier than the number the scale showed a day earlier.
This is why the sauna almost never works alone. It sits at the tail end of a longer process that also manipulates food, sodium, and total water intake. The UFC Performance Institute has stated that a fighter can lose roughly 10 percent of total body mass during fight week when it is managed properly, though it warns that this should come from a staged approach to gut content, stored carbohydrate, and body water, not from sweating in a sauna until the number drops.
How a sauna cut works
The mechanism is simple. A traditional sauna runs hot, usually 80 to 100 degrees Celsius according to strength coach James de Lacey of Sweet Science of Fighting, and that heat raises the body’s core temperature until it responds by sweating. Every liter of sweat is close to a kilogram off the scale.
How fast does it come off? Under typical sauna conditions, the body sheds somewhere around 0.5 to 1.0 kilograms of water per hour, or roughly 1 to 2 pounds, according to sweat-loss figures compiled by sauna manufacturer Smartmak from Finnish sauna research. Fighters who have water-loaded earlier in the week, flooding the body with fluid so it flushes faster, sometimes report quicker losses once the tap is turned off.
A sauna cut is the last step in fight week, not the first. It usually comes after days of water loading and a final fluid restriction. Fighters work in short bouts with breaks, checking a scale as they go, rather than sitting through one long stretch. They stop at the exact number. Every ounce lost has to go back before the fight.
Sauna cut vs. hot bath vs. sauna suit
Most confusion around the sauna cut comes from the other heat methods fighters talk about in the same breath. A hot bath and a sauna suit do the same job through different means. All three raise core temperature and force the body to sweat out water. The difference is the environment.
| Method | How it works | Where it happens | Notes |
|---|---|---|---|
| Traditional sauna | Dry heat at 80 to 100°C raises core temperature | A sauna room at a gym or facility | The classic method; needs access to a hot sauna |
| Hot bath | Hot water immersion, often with Epsom salt added, traps heat against the skin | A bathtub, at home or in a hotel | Fighters can control the water temperature; salt is added to draw out more sweat |
| Sauna suit | An insulated suit worn during movement traps body heat and sweat | Anywhere the fighter can move or rest | Portable; often used for the final pounds when a sauna is not available |
The takeaway is that these are variations on one idea. A fighter picks whichever heat source is available and comfortable, and many use a combination across a single cut.
Is a sauna cut safe?
This is where a sauna cut stops being a simple definition and becomes a subject of real medical and regulatory concern. Deliberate dehydration carries genuine risk. The immediate dangers include dizziness and heat illness, plus strain on the kidneys and the heart. That risk climbs the more weight a fighter tries to lose, and the faster they try to lose it.
The scale of the problem shows up in the data. Research tracking UFC athletes found that roughly 39 percent of MMA fighters compete while still dehydrated, according to figures reported by Fight Metrics Pro. In the most serious cases, weight cutting has killed. The Conversation notes that at least one MMA death has been formally linked to weight cutting in medical case reports, including the death of Yang Jian Bing, who died in 2015 from heart failure while dehydrating to make weight.
Regulators have responded. ONE Championship banned dehydration-based weight cutting outright after fighter deaths, as reported by BodySpec citing MMA Fighting. In the United States, the California State Athletic Commission flags any fighter who regains 15 percent or more of their body weight between the weigh-in and fight day, and it extended the weigh-in window to 30 hours to give fighters longer to recover, according to ESPN and Fox Sports. Boxing has gone further in places. The British Boxing Board of Control bans sauna use for weight cutting entirely, and in 2025 an opponent was pulled from his bout with Adam Azim for using one, as reported by BBC Sport. Intravenous rehydration, once a fast way to recover fluids after the scale, is now banned under anti-doping rules.
Common misconceptions
The biggest misconception is that the scale drop represents weight loss in any lasting sense. It does not. A sauna cut removes water, and the moment a fighter rehydrates, the fluid returns and the weight comes back with it, as Smartmak and other sources on sauna physiology point out.
A second mistake is assuming more time in the heat is always better. Past a certain point, the body becomes too dehydrated to sweat effectively, and core temperature keeps climbing, which is how fighters end up with heat illness on a sauna floor. Longer is not safer.
Finally, the “safe 10 percent” figure gets misread. That number from the UFC Performance Institute assumes a staged cut across gut content, glycogen, and water under supervision. It is not a green light to dump 10 percent of body weight through sweat alone.
Frequently Asked Questions
How much weight can you lose in a sauna?
Around 1 to 2 pounds of water per hour under typical conditions, sometimes more for a fighter who has water-loaded first. That is temporary water loss, not fat.
Do MMA fighters cut weight in the sauna?
Yes. The sauna is a standard fight-week tool, usually saved for the final pounds before the weigh-in once other methods have already done most of the work.
Does the weight come back after a sauna cut?
Yes, and fast. The loss is water, so rehydrating and eating put it right back, usually within a day, which is exactly why a fighter weighs more in the cage than on the scale the night before.
Is cutting weight in a sauna dangerous?
It can be. How much danger there is depends on the size and speed of the cut, and several organizations now restrict or ban dehydration-based cutting because of it.
Is a sauna cut the same as losing weight?
No. A sauna cut lowers body water for a day to make a weight class. It is not fat loss, though the two get confused because both change what the scale reads.
Sources
- UFC Performance Institute. “Weight Cutting and Fight-Week Fueling,” Cross Sectional Performance Analysis and Projection of the UFC Athlete, Vol. 2 (via Combat Sports Law). Accessed August 2026.
https://combatsportslaw.com/2021/05/17/ufc-performance-institute-claims-fighters-can-safely-lose-10-body-mass-during-fight-week/ - Fight Metrics Pro. “How UFC Weigh-Ins and Weight Cuts Affect a Fight and the Odds.” Accessed August 2026.
https://fightmetricspro.com/blogs/fight-metrics-pro/how-ufc-weigh-ins-and-weight-cuts-affect-a-fight-and-the-odds - ESPN. “Seven UFC 298 fighters flagged for rehydration issue.” Accessed August 2026.
https://africa.espn.com/mma/story/_/id/39610394/seven-ufc-298-fighters-flagged-rehydration-issue - The Conversation. “Mixed martial arts and the danger of extreme weight cutting.” Accessed August 2026.
https://theconversation.com/mixed-martial-arts-and-the-danger-of-extreme-weight-cutting-162569 - BBC Sport. “Eubank to face BBBofC over sauna use in weight cut.” Accessed August 2026.
https://www.bbc.com/sport/boxing/articles/c5yx160kd27o - BodySpec. “Weight Cutting: A Safe Guide for Combat Athletes.” Accessed August 2026.
https://www.bodyspec.com/blog/post/weight_cutting_a_safe_guide_for_combat_athletes - Smartmak. “How much water weight you lose in a sauna session.” Accessed August 2026.
https://www.smartmak.com/en_ca/blog/how-much-weight-do-you-really-lose-in-a-sauna-session/ - Sweet Science of Fighting. “Is The Sauna Good For MMA?” Accessed August 2026.
https://sweetscienceoffighting.com/is-the-sauna-good-for-mma/
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