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Glycerol: banned for 8 years, then not
Prohibited from 2010 as a masking agent. Removed from the List with effect from 1 January 2018. Many fighters still believe it is banned, and a smaller number are using it without knowing why it was ever a question.
What it does is hold fluid in the body. Which sounds like the last thing anyone in a weight-class sport would want, until you think about which side of the scale you are on.
The anti-doping history, because it still confuses people
WADA added glycerol to the Prohibited List in 2010, under S5, Diuretics and Masking Agents. The concern was plasma volume expansion. If glycerol dilutes blood, it could in theory blunt the markers used to detect blood doping and distort the Athlete Biological Passport.
Laboratories developed urinary thresholds to separate what a body makes and eats from what an athlete has taken deliberately.
Then it came off. WADA's own explanation for the 2018 List states that, in consideration of scientific articles published since 2012 addressing glycerol's ability to influence plasma volume and Athlete Biological Passport parameters, the magnitude of the glycerol-derived effects is regarded as minimal.
On that basis it was removed.
A substance sat on the Prohibited List for 8 years on a mechanism that the subsequent research did not support. That is the system working, in the sense that evidence accumulated and the position changed. It is also a reminder that the List is a document with a revision history rather than a fixed set of facts.
Which is why confirming the current rules governing your bout is worth doing every year, and why nothing on this page substitutes for checking.
What glycerol does in the body
Glycerol is osmotically active. Taken with a large volume of fluid, it increases the amount of that fluid the body retains rather than passes as urine.
In endurance research, glycerol hyperhydration has been associated with retention of around a litre or more of additional fluid, with reductions in heart rate and core temperature during exercise and improvements in endurance performance.
The effects are described as most relevant to events lasting beyond 60 to 90 minutes, particularly in heat.
One controlled study gives a sense of the magnitude. Nine trained men took a hyperhydrating mixture twice daily for 7 days containing 1.0 g per kilogram of glycerol, 10 g of creatine and 75 g of glucose.
Body mass rose by about 1.1 litres' worth and total body water by about 1.0 litre.
Note that the mixture contained creatine and glucose alongside the glycerol, so that study does not isolate glycerol's own contribution.
The obvious problem
You are reading this as somebody who spends 8 weeks removing water and sodium so a number on a scale will be lower.
A supplement that adds a litre of retained fluid is, in fight week, a supplement that adds a kilogram to the weigh-in. There is no clever framing that gets around that.
After the scale it becomes a different question again, because a rehydration clause measures what you weigh the next morning and does not care how the weight got there.
So during the cut, glycerol is an obstacle you would be paying for.
Where it becomes interesting
The moment you step off the scale, everything inverts. The job stops being removal and becomes retention, and it has to happen fast.
The whole difficulty of post-weigh-in rehydration is that a large volume of fluid drunk quickly leaves as urine before it reaches the compartments that need it.
That is precisely the problem glycerol is documented to affect.
So the logic is clean. A compound that increases fluid retention, applied in the window where fluid retention is the entire objective.
That is reasoning, not evidence. The research on glycerol hyperhydration was done in endurance athletes preparing for prolonged exercise in heat, not in fighters recovering from a rapid weight loss.
I could not find a controlled trial of glycerol in post-weigh-in rehydration in combat sport.
The mechanism transfers on paper. Whether it produces a meaningful benefit in that specific window, at doses that do not cause gastrointestinal problems, on a fighter with hours rather than days, nobody has tested.
The second application, which is better supported
Fighting in heat. The endurance evidence sits closer to this one, because the documented benefits of lower heart rate, lower core temperature and better endurance were measured under exactly those conditions.
A fighter competing in a hot venue, or training through a camp in a hot country, is nearer to the population the research was done in than a fighter rehydrating after a scale.
Though the same caution applies to timing: heat acclimation and the weight cut already pull in opposite directions, and adding a fluid-retaining compound to that calendar needs planning rather than improvisation.
Practical, with the caveats attached
It is permitted, and has been since the start of 2018. But private testing programmes can set their own rules, and lists are revised every year.
Check the document governing your bout rather than this page.
Never during the cut. The mechanism works against you and the cost is measured on the scale.
If trialling it, do so in camp and away from any weigh-in. Side effects at normal doses are described as mild: bloating, nausea, headache in some people.
Mild is not nothing when the alternative is finding out on a fight night.
Do not treat it as a substitute for the basics. Sodium, carbohydrate and time do most of the work in rehydration, and they have direct evidence behind them in this sport.
Glycerol would be an addition at the margin, not a replacement for a plan.
Buy certified. Same rule as everything else. Strict liability applies to the contents of the tub, not to the label.
What I actually think
Of the supplements in this cluster, glycerol is the one where I am least willing to give you a protocol, and that is deliberate.
The evidence exists but it was collected in a different sport, for a different purpose, in athletes in a different physiological state.
The application that would matter most to a fighter is the one nobody has studied.
It belongs on the list because a fighter should know it is permitted and know what it does. It does not belong in a fight plan on the strength of what is currently published.
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+. Hyperhydration protocols involve large fluid volumes and are not appropriate for everyone. Anyone with kidney, cardiac or blood pressure conditions, or taking medication affecting fluid balance, should speak to a physician first. Prohibited lists are revised annually and private testing programmes may differ from the WADA List; always confirm the current rules governing your competition.