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Rehydration after the weigh-in: the hours that decide the fight
Fighters plan the cut for 8 weeks and improvise the recovery in 8 hours. Then they wonder why the legs went in round four. The scale is halfway. What happens after it decides how much of you actually turns up.
Straight off the scale, 500–600 ml of an oral rehydration solution: sodium and glucose together, because they cross the gut wall together and water follows.
Then small volumes, repeatedly. Not one bottle.
Carbohydrate next, in quantity, spread across the 24 hours. Every gram of glycogen stored pulls about 3 grams of water in with it.
That store is also what the later rounds run on, which is the other reason this window matters.
Total fluid around one and a half times what you removed, because you never keep all of what you drink. Protein waits half an hour.
Almost nothing gets written about this part, because it is not dramatic. How much you are allowed to put back can also be capped by the rules or by your contract.
One route back is closed before you start. Diuretics sit in category S5, prohibited at all times, and the contamination route into a positive test runs through products that never mention them.
Nobody films the recovery. But between two fighters who made the same weight, the one who rehydrated properly is a measurably different athlete by the first bell.
One fighter did, once. Alex Pereira filmed himself at 230 the day after weighing 204.5 for UFC 303, about 25 pounds back in a day, and his full record shows what a rebound that size sits on top of.
Why plain water does not work
The instinct after the scale is to drink. A litre, fast, because you have been rationing sips for 2 days.
One method is not available to you regardless of how far behind you are. Infusions above the permitted volume are a prohibited method whatever is in the bag, and the rule is in IV drips.
It does not do what you think. A dehydrated body has lost fluid and the sodium that was dissolved in it.
Pour plain water into that and you dilute what sodium remains further. The body reads the drop in concentration as a signal to get rid of the excess, and a large part of what you just drank leaves as urine within the hour.
You feel briefly full, you visit the toilet repeatedly, and your blood volume barely moves.
Sodium is what lets fluid stay where you need it. That is the entire reason oral rehydration solutions exist and the reason they are the first thing off the scale: water alone leaks.
Fluid with sodium and glucose together first, in small repeated volumes. Then carbohydrate in quantity. Then normal food. In that order, on a clock, not all at once because you are thirsty.
The order that works
1. Fluid with sodium and a little sugar. Straight off the scale, around 500–600 ml of an oral rehydration solution. Those solutions contain glucose as well as salt for a physiological reason: sodium and glucose are absorbed together across the gut wall, and water follows them. That is why an ORS rehydrates faster than salt water and much faster than plain water. So do not strip the carbohydrate out of this step in the belief that sodium alone is the active ingredient. Then keep going in small repeated volumes rather than one large bottle. The gut absorbs a steady stream far better than a flood, and a flood in a shrunken stomach comes back up more often than fighters admit.
2. Carbohydrate, in quantity. Once fluid is moving, the job changes from absorption to refilling. Carbohydrate does two things at once: it restores the glycogen you emptied deliberately, and every gram of glycogen stored pulls roughly 3 grams of water into the muscle with it. This is why carbohydrate is a rehydration tool and not just fuel.
Aim for a substantial load spread across the next 24 hours rather than one enormous meal.
One compound that increases fluid retention, glycerol, has been permitted since 2018, though nobody has tested it in this particular window.
3. Normal, familiar food. Once the first two are underway. Plain, tested, boring. The rice you have eaten all camp.
Protein waits. Not forever. But it is not the first thing in. Give it half an hour or so while fluid and fast carbohydrate do the urgent work.
How much fluid, actually
More than you lost. That sounds wrong, and it is the point most fighters miss.
You never retain 100% of what you drink. Some leaves as urine no matter how well you do it. So replacing exactly the weight you dropped leaves you still short. A workable target is around one and a half times the fluid you removed, spread across the recovery window. That figure is not folklore: the Sports Dietitians Australia position statement puts it at up to 150% of the net deficit when a moderate to severe loss has to be reversed quickly, because losses continue while fluid redistributes. The calculator on this site works that figure out from your own numbers, along with a carbohydrate target for the 24 hours after the scale.
Spread is doing as much work in that sentence as the number. One and a half times your losses drunk in the first hour buys you a bad night and a heavy warm-up, not recovery.
The same statement flags something fighters run into constantly. Drinking large volumes is genuinely hard after significant heat strain or when gut function has been disturbed, and both describe a man who has just come out of a hot bath.
Plan for the volume to be difficult, not for willpower to solve it.
What the position stand specifies
Until 2025 there was no consensus document written for this sport. There is now, and it puts numbers on the protocol above.
The International Society of Sports Nutrition position stand on nutrition and weight cut strategies for mixed martial arts and other combat sports was published in March 2025.
Its recommendations for the hours after the scale run as follows.
| What | The figure |
|---|---|
| Oral rehydration solution, immediately post-weigh-in | 1 to 1.5 litres per hour |
| Sodium concentration in that solution | 50 to 90 mmol/L |
| Fast-acting carbohydrate, following the ORS | Up to 60 g per hour, and no more |
| Total carbohydrate after significant glycogen depletion | 8 to 12 g per kg of body mass |
| Total carbohydrate after modest restriction | 4 to 7 g per kg |
| Fibre, post-weigh-in | Limited, to avoid gastrointestinal distress |
| Target regain | At least 10 percent of body mass |
Two of those deserve a second look.
Sixty grams of carbohydrate an hour is a ceiling. It is set by what the gut can absorb, whatever the muscle wants, and going beyond it speeds nothing up. All it buys is nausea in a stomach that has been empty for 2 days.
The 10 percent regain figure is higher than most fighters achieve. On 70 kg that is 7 kilograms back, and the stand frames it as the level at which performance decline and the negative effects of rapid weight loss are mitigated. A fighter who comes off the scale and puts 3 kilograms back has not completed the job, whatever the mirror says. Whether that regain is worth chasing depends on the format you are fighting in, which is the section below.
One note on the published text. The sodium range appears in the position stand as mmol/dL, which would describe a solution nobody could drink.
The figure that makes physiological sense, and that matches standard oral rehydration formulations, is 50 to 90 mmol per litre.
How far back is far enough
The position stand tells you what to drink. It does not tell you when to stop, and that number exists.
The practical target from the combat sport literature is to come back to within about 2 percent of the body mass you carried before the cut started. Below that gap the measurable performance cost of being dehydrated is small. Above it, the cost rises, and no amount of good intention in the warm-up removes it.
The fluid arithmetic behind that target is the 125 to 150 percent rule: to reverse a deficit you have to drink more than the deficit, because urine losses continue while the fluid redistributes. The lower end is enough after a modest loss. The upper end is for a loss that was large and has to be reversed in a hurry, which is the fighter's case.
There is a second number, and it belongs to the week before rather than to the hours after. When the weigh-in is on the morning of competition, the recovery window is too short to reverse a large deficit, whatever you drink. The recommendation in that format is not to need it: keep the part that comes off through dehydration under about 3 percent of body mass, and build the rest of the gap into camp. The same-day weigh-in page sets out what that means for the cut itself.
Put the three together and the plan reads: know the deficit, drink 125 to 150 percent of it across the window you have, and finish within 2 percent of where you started. If the arithmetic does not reach 2 percent, the problem was the cut, not the refill.
Does the regain actually decide the fight?
Two studies from the same Australian group looked at real competitions rather than laboratories, and they disagree in a way that is worth understanding.
In judo, at a real tournament, the athletes who put more body mass back on between the weigh-in and their matches did better. In a multi-day boxing tournament, the same measurement showed no such link.
My reading of the pair: the refill matters most where the format gives you one recovery window and one decisive day. In a tournament that runs across several days, what decides the result is what you can repeat, and a large first-day refill does not carry across to the third morning. The tournament page covers what repeating it looks like.
The honest limit on both studies is that they describe what happened, not what caused it. A fighter who regains 7 kilograms may be the fighter whose camp was better run in the first place.
The whole thing on one screen
Everything above, as a schedule. This is the version to have open on the day rather than the reasoning behind it.
| From the scale | Fluid | Food | Volume |
|---|---|---|---|
| 0 to 30 min | Oral rehydration solution, sipped. Never plain water first. | Simple carbohydrate only, 50 to 80 g. No protein. | 500–600 ml |
| 30 to 90 min | ORS continuing, plus diluted juice | Banana, rice cakes, honey | 500–700 ml |
| 90 min to 3 hr | Sports drink, or water with electrolyte | First full meal: 150–200 g carbohydrate with protein | 700–900 ml |
| 3 to 6 hr | Water, with sodium coming from the food | Second meal, larger. Cooked vegetables, no raw. | 600–800 ml |
| 6 to 10 hr | Water, sipped as needed | Top up. Do not overload. | 400–600 ml |
Total across the window: roughly one and a half times what came off. Two kilograms lost means about 3 litres in, spread rather than poured.
Checking whether it worked
Three signs, and none of them is how you feel.
| Sign | What you want | What it means if you do not have it |
|---|---|---|
| Urine colour | Pale yellow by hour four or five | Clear means you are running fluid through without holding it. Dark means you are behind. |
| Cramp at rest | None | Electrolytes rather than volume. More plain water makes it worse. |
| Weight back on | Most of what came off, by fight morning | If the scale has barely moved, the fluid is not being retained and the sodium is the first thing to look at. |
Clear urine is the one people misread. It looks like success and it is the opposite: fluid passing straight through rather than being held, which is what happens when water arrives without sodium.
Day-before: the 24-hour version
With a weigh-in the day before, you have room to do this properly.
- First 30 minutes. Oral rehydration solution, 500–600 ml. Sit down. No protein yet.
- First 2 hours. Continue fluid in small volumes. Introduce fast carbohydrate. Nothing heavy.
- 2 to 6 hours. First proper meal: familiar carbohydrate base, moderate protein, low fat, low fibre. Fluid continues alongside.
- Evening. Second meal, same principles. Fluid continues.
- Overnight and fight morning. The remaining carbohydrate load, normal meals, tapering fluid so you are not up all night.
Two checks that tell you it is working, without any equipment: urine colour returning toward pale through the evening, and body weight recovering toward your normal walk-around figure by morning.
If both are flat, you are behind, and you have a few hours left to fix it.
Same-day: the compressed version
If you weigh in on fight morning, none of the above fits. The window is a few hours and part of it is warm-up.
- Off the scale. Around 500 ml of oral rehydration solution.
- Then fast carbohydrate only. Nothing heavy, nothing high in fat or fibre, and nothing you have not already eaten before a hard session in camp.
- 45 to 90 minutes. A small meal, familiar and plain.
- From 30 minutes before the walk. Sips.
Put it plainly: in this format you are not recovering, you are limiting damage. Which is exactly why the water cut has to be a fraction of what it would be with a day in hand: see why same-day weigh-ins change the whole plan.
The celebration meal after the weigh-in has cost more fights than any training injury. A shrunken gut, 2 days of near-fasting, and then a large unfamiliar restaurant meal. The result is a fighter who spends the night before the fight in the bathroom instead of asleep.
Nothing new in fight week, not a food, not a drink, not a supplement handed to you at the venue.
The mistakes that undo the refill
Do not take an intravenous drip. This one has ended careers rather than fights. Intravenous infusions above a set volume are prohibited as a method under the World Anti-Doping Code. Regardless of what is in the bag. Saline counts. There is no prohibited substance involved and it is still a violation, permitted only with a Therapeutic Use Exemption or during a documented hospital admission.
A drip after the scale is the most avoidable anti-doping case in combat sports.
Do not reach for anything new from the supplement bag. Fight week is when fighters accept things they would normally check. Whatever goes in has to be certified and logged like everything else.
The reasoning is in can a supplement make you fail a drug test.
Do not chase the scale back up. Regaining every kilogram by fight time is not the goal and is not achievable in most formats. The goal is blood volume, muscle glycogen and a gut that is working.
A number on a bathroom scale the next morning tells you very little about any of the three.
Why an oral rehydration solution and not water, what is actually in the sachet, and why the sugar-free tablet from the cut stops working here: electrolytes and ORS.
On magnesium specifically, including why it stays in the evening and stops on fight morning, and what the cramp evidence actually shows: magnesium for fighters.
How much comes back overnight, measured on fight night across three UFC cards, is in how much weight UFC fighters gain after the weigh-in.
Two complete sample documents are free to read before you buy anything.
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Oleksandr Foka is a sports nutritionist with over a decade in professional sport. He wrestled freestyle from the age of 4 until he was 22, competing as a medallist and champion at Ukrainian and international level, and has worked with amateur boxers since 2017, including champions and medallists at world championships. He has worked in world title camps in boxing with Oleksandr Usyk, Oleksandr Gvozdyk, Denys Berinchyk, Vladyslav Sirenko, Murodjon Ahmadaliev, Israil Madrimov, Sergiy Bogachuk, Sabirzhan Akkalykov and Abylaikhan Zhussupov, and with the Kazakhstan national boxing team and with Kazakhstan judo athletes, and currently works on the WTA tour.
Oleksandr Foka — sports nutritionist. Questions: fokaoleksandr@gmail.com
Educational content, not medical treatment. For adults 18+. Weight cutting and rehydration carry real risks including electrolyte imbalance and cardiac strain. Nothing here replaces care from a physician. Extreme cuts require supervision by a physician and a qualified specialist.