How do UFC fighters cut weight?

Most descriptions of a UFC weight cut start with the sauna. In a well-run fight week the sauna comes last, if it comes at all, and by then almost everything is already off.

Each stage removes something different, and each one has a point where it stops taking weight off the body and starts taking it out of the fighter. The order is what keeps those points apart.

Below is the sequence the research supports, then what surveys say fighters actually do, which is rougher, and one documented cut that went too far. How much all of it adds up to has its own page, with the numbers from three world title camps.

Camp: the weight that has to be gone before fight week

Fight week only ever removes the last few percent. Everything above that has to leave during camp, as fat, at a pace the fighter can still train through.

The most detailed recent look at how professionals manage this followed 33 professional MMA fighters through 80 fights, with dietitians on site encouraging evidence-based practice. Most of them lost weight gradually across camp, and all of them cut in the final days. Many lost fat-free mass during the camp phase, and the slowest rates of loss preserved it best.

One finding from that study matters more than the rest for planning. Body weight 7 to 10 days out told the researchers more about how much a fighter would put back after the weigh-in than dehydration in the last 24 to 48 hours did.

So the shape of the cut is largely set before fight week begins. A fighter who arrives at the final week with too much still to lose has already made that week risky, however carefully the last days are run. How much can come off in a single week is a smaller number than most people assume.

One public example of a large gap spread across a long camp is Kayla Harrison's cut to 135, and a case where the fat ran out first is TJ Dillashaw's drop to 125.

Early in fight week: the water load

This is the stage most fans have heard of. For several days the fighter drinks far more than usual, then cuts intake sharply. The controlled research protocol runs at about 100 ml per kilogram of body weight per day. The theory is that the kidneys keep excreting at the raised rate for a while after intake drops, and that water leaves with it.

The weight comes off. Why it comes off is less settled than the confidence around it suggests, and one real risk gets overlooked: drinking at that volume without enough sodium can dilute the sodium in the blood. What the trials actually showed is covered separately.

The final days: carbohydrate, fiber and sodium come down

Carbohydrate is the biggest lever here. Glycogen, the carbohydrate stored in muscle and liver, holds water with it, roughly 3 to 4 grams of water for every gram. Run the stores down over the last days and that water goes too. It is also the stage whose cost shows up in the fight if the stores are not refilled, which is why refilling them is one of the first jobs after the scale.

Fiber drops at the same time. Food residue in the gut has weight, and a low-residue diet for the final days removes some of it without touching body water or muscle. The amount is small, and it is the cheapest weight in the whole process. How much it is realistically worth.

Sodium comes down as well, which reduces the water the body holds on to.

The authors of the 2024 study describe the same staged order: carbohydrate, fiber and sodium, then fluid last. Their stated reason is the one that matters. Every gram removed this way is a gram that does not have to be sweated out on the final day.

Last: fluid, then sweat for whatever is left

By the final day intake is restricted, and what remains comes off as body water. How much remains depends on everything above.

Sweat is the crudest tool, and it belongs at the very end, for a small remainder. Saunas, hot baths, training in a plastic suit. In a 2022 crossover trial, 13 male MMA athletes sat in hot water at about 40 °C for 20 minutes, then lay wrapped in a heated blanket for 40, twice in a row. Adding Epsom salt to the water bought nothing measurable. What heat actually removes.

In the cruiserweight camps I ran, the final 24 hours had no sauna, no suit and no training. Food calculation and water, nothing else. The detail is in the article on those three cuts.

The weigh-in: 9 to 11 in the morning, and 1 pound

UFC official weigh-ins happen the day before the fight, between 9 and 11 a.m. local time. Depending on the commission, a fighter who misses on the first attempt can be given up to an extra hour. The staged appearance later that day is ceremonial and records nothing.

Non-title bouts carry a 1-pound allowance, so a lightweight can weigh 156. Title bouts carry none, and 155 means 155.

Missing has three usual outcomes. The fighter forfeits part of the purse to the opponent, commonly 20 percent and sometimes 30. The bout goes ahead as a catchweight if the opponent accepts. Or it is canceled. In a title fight a challenger who misses cannot win the belt, and a champion who misses can lose it on the scale.

The morning format dates from June 2016, and it was introduced to give fighters more time to recover. In the 2 years either side of the change, the share of fighters missing weight rose from 5.7 to 8.4 percent. Why extra recovery time produced worse weigh-ins is the most useful thing to understand about the whole process, and what missing actually costs goes beyond the fine.

The 30 hours after

Everything taken out now has to go back in, by mouth. Fluid with sodium first, then carbohydrate in quantity to refill glycogen, then ordinary food the fighter's stomach already knows. The International Society of Sports Nutrition published a position stand on exactly this in March 2025, and its targets are laid out here.

The IV bag is not part of it. Under the UFC's anti-doping program, as under the WADA list, intravenous infusions above 100 ml in any 12-hour period are a prohibited method, whatever the bag contains. The UFC's version allows an infusion that a licensed physician judges medically necessary and a licensed professional gives. Before the ban arrived in 2015, IV rehydration after the weigh-in was routine for elite fighters. The ban ended it. The cases decided on plain saline.

How much comes back varies widely. A UK study followed 7 MMA fighters through a competition week. They lost 5.6 kg on average, about 8 percent of body mass, before the weigh-in and put back 7.4 kg in the 32 hours after it, so they fought heavier than they had been at the start of the week. At the official weigh-in 4 of the 7 were dehydrated by urine measures and the other 3 severely dehydrated.

What fighters say they actually do

The sequence above is the version with evidence behind it. Asked directly, fighters describe something rougher.

The largest survey in the sport covered 314 MMA athletes, professional and amateur, across 9 weight categories from strawweight to heavyweight. Almost everyone cut: 97.2 percent of the 287 men and all 27 women. Professionals cut harder. In the final week professional men lost 5.9 percent of body weight against 4.2 percent for amateurs, and 3.7 percent in the last 24 hours alone.

A second survey, of 637 athletes across 7 combat sports, found MMA fighters the heaviest users of the sauna, at 76 percent, and of water loading, at 67, with the second-highest use of rubber or plastic suits, at 63.

Water loading shows up in both versions. The sauna and the suit are supposed to be a small remainder on the last day, and in these surveys they are main tools. When the men were asked who shaped how they cut, the most common answer was the coach, at 29.3 percent. Among the women it was 48.1 percent.

Where it breaks

The clearest record of an extreme cut is a 2019 case study of an elite male MMA fighter measured across 8 weeks. His plan: 7 weeks eating 1,300 to 1,900 kcal a day, then 5 days of water loading at 8 liters a day for 4 days and 250 ml on the fifth, then 20 hours of fasting and dehydration, then 32 hours to rehydrate and refuel.

He went from 80.2 kg to 65.7, a loss of 18.1 percent of body mass. The final 24 hours alone took 9.3 percent. The researchers recorded the signs of relative energy deficiency: a resting metabolic rate 331 kcal a day lower, suppressed testosterone, performance tests he could not finish. The dehydration at the end pushed his blood sodium above the normal range and caused acute kidney injury.

One athlete, measured closely. The surveys above describe the same methods in use by hundreds.

The sport has lost fighters to this. In 2013 a Brazilian flyweight, called in on short notice, collapsed in a sauna hours before his weigh-in and died in hospital. In 2015 a Chinese fighter died after a dehydration cut, and ONE Championship replaced dehydration cutting with hydration testing at its weigh-ins. How ONE regulates the other end of the week, and the signs that a cut has gone past water.

In the UFC itself, Khabib Nurmagomedov's cut for UFC 209 ended in hospital the night before the weigh-in.

Six public cases, compared side by side: weight cut case studies.

If you are planning your own

Start from the gap. The distance between walk-around weight and the limit, and the days available to close it, decide whether any of the stages above are safe at all. The calculator runs that arithmetic for your own weight and weigh-in format.

A large gap is answered with more weeks of camp or a different division, and choosing the division comes before any of the stages above.

Common questions

How do UFC fighters cut weight so fast?

Most of the fight-week loss is water, gut content and the water stored with glycogen, removed in stages over the final days with fluid restricted last. The fat comes off earlier, across camp.

How much weight do UFC fighters lose in fight week?

In the largest survey of MMA athletes, professional men lost 5.9 percent of body weight in the final week and 3.7 percent in the last 24 hours. Individual cuts range widely around those averages.

Can UFC fighters use an IV after the weigh-in?

Not for routine rehydration. Under the UFC's anti-doping program, intravenous infusions above 100 ml in any 12-hour period are a prohibited method whatever the bag contains, with a narrow exception for infusions a licensed physician judges medically necessary.

What happens if a UFC fighter misses weight?

Usually the fighter forfeits part of the purse to the opponent, commonly 20 percent and sometimes 30, and the bout goes ahead as a catchweight if the opponent accepts. A challenger who misses cannot win the title, and a champion who misses can lose it.

Do UFC fighters still use saunas to cut weight?

Many do. In a survey of 637 combat sport athletes, 76 percent of the MMA fighters reported using the sauna, more than in any other sport studied. A planned cut tries to leave as little as possible for sweat.