Weight Cutting in Combat Sports: What, Why and How?

In combat sports, a heavier athlete has the potential to create more force against their opponent simply through their size. Weight classes are designed to remove this potential advantage, as athletes compete against others weighing in at a similar bodyweight.

Athletes originally started weight cutting to ‘get back’ some of this advantage by enabling them to compete in a weight class below the bodyweight they walk around at. Nowadays– according to some studies – up to 100% of competitors engage in weight cuts pre-competition, meaning it is less about gaining a size advantage and more about trying to avoid a size disadvantage (Barley, Chapman and Abbiss, 2019; Connor and Egan, 2019; Park et al., 2019).

So what exactly is weight cutting? It is rapid weight loss (RWL) achieved primarily through reducing total body water, stored carbohydrate (glycogen) and gut contents. Using these techniques athletes might drop up to 3 weight classes in the 7-10 days pre-competition weigh in (Matthews and Nicholas, 2017)! Between the weigh in and the fight athletes attempt rapid weight regain (RWG) to restore their body water and carbohydrates in time for the fight.

The challenge is undertaking RWL in a way that avoids or minimises an adverse impact on health and performance. If done incorrectly, the consequences can be severe. Athletes have died because of extreme water loss techniques, and many more have been forced to withdraw from competition through health complications.

Despite the history and prevalence of weight cutting, we have relatively little direct research on the effectiveness of different RWL and RWG techniques, their relative risks, and potential performance impacts. Our understanding is drawn primarily from self-reported data from athletes and their support team, which is known to be at high risk of containing inaccurate information. In addition, as any one athlete typically uses multiple RWL and RWG techniques, it is not possible to determine the relative role of each technique on total weight lost and regained and performance from self-reported data. Plus, many other factors also have the potential to impact fight performance and outcome, which can muddy the findings of even the most robust study … let alone simple self-reported data. These factors include general health, pre-weight cut weight loss, experience, technical skill, and psychological state … plus the state of all these in the fighters opponent!!

This article looks at some of the techniques used in RWL and RWG, considerations for health and performance, differences between males and females, and highlights some of the (many) unknowns that remain in our understanding.

Rapid Weight Loss (RWL)

In the literature, RWL of 2-10% of bodyweight is typically reported (Crighton, Close and Morton, 2016; Connor and Egan, 2019; Parks et al., 2019). The largest weight cuts appear to be seen in MMA and boxing. This is perhaps not surprising as these athletes typically compete less regularly (and so might be more able to ‘afford’ a larger recovery period post fight) and have a longer period of 24-36 hours between weigh in and their fight to restore weight (RWG).

As noted above, RWL is characterised by techniques aimed to reduce gut contents, deplete stored carbohydrates and reducing total body water.

Looking at each in turn …

Reduce Gut Contents

Our guts contain fibre and other residue from the food we eat, and this can weigh between 0.5-2kg. Some athletes use laxatives to clear this, however this is considered a more extreme measure and has potential health complications (e.g. subsequent constipation).

An alternative is to restrict the fibre and residue in the diet in the 3-4 days before weigh in, which gives time for the contents sitting in there from previous days to clear naturally. Despite the fact this is considered the RWL strategy with the lowest health or performance risk, it is not employed by all athletes undertaking RWL (Connor and Egan, 2019; Parks et al., 2019)!

Of course, this is all assuming the athlete has a diet rich in fibre and residue. If they eat few fruits, vegetables, wholegrains, nuts, seeds and / or legumes there will not be much in their gut to clear!

Low carbohydrate diets

More than 50% of athletes may restrict carbohydrate intake to enable their stored carbohydrate to be gradually depleted in the days preceding weigh in, reducing body weight (Conor and Egan, 2019; Parks et al., 2019). As with the low residue diets, how much weight can be lost via this technique is going to depend on how ‘carb loaded’ the athlete was going into the weight cut. If they had been on a low carbohydrate diet as part of a fat loss diet in the preceding weeks they will have limited carbohydrate (and therefore weight) to lose this way. In addition, in the week before the fight the athlete may be tapering their training … they must consider if they are going to be doing enough activity to deplete their muscle carbohydrate stores.

Reducing total body water

Athletes may reduce total body water through restricting fluid intake, low sodium diets, water loading, thermal strain (sweating), and even spitting.

Of the techniques that involve fluid restriction, water loading has gained increasing popularity. Between 57-90% of athletes reported using it to cut weight in recent studies (Crighton, Close and Morton, 2016; Matthews and Nicholas, 2017; Connor and Egan, 2019; Parks et al., 2019). The technique is aimed at increasing fluid losses by preceding the period of restricted fluid intake with a period of high water intake (aka water loading). However, until a recent study by Reale et al the efficacy and safety of water loading had not been directly tested (Reale et al., 2018). In their study, water loading had a mean increase in weight loss of 0.6% bodyweight compared to fluid restriction alone with no adverse impact on health markers or tested performance metrics. These results are promising. The reader is referred to their study to understand the study and its application in practice in more detail.

Athletes may spend time in saunas, training in sweat suits or heated rooms, and hot salt baths to induce thermal strain and sweat losses. In recent studies by Parks, and Connor and Egan, over two thirds of the 120 athletes who reported undertaking RWL used one or more of these measures (Conor and Egan, 2019; Parks et al., 2019). If performed to extreme, these techniques can risk heat stroke, perfusion, physical burns and severe medical dehydration. For most of these techniques there is little research on ‘best practice’. Of most interest is a 2020 study by Connor et al that tested a hot water bath protocol with and without the use of salts (Connor, Shelley and Egan, 2020). It was interesting to note that equivalent weight loss was observed with or without the addition of salt. Although the salt concentration of the water was low, it was a concentration in the bounds of what many athletes report using. I would recommend reading the study to understand the details of the protocol and how it may be applied in practice.

Sweat rates do vary by individual, which will impact how easily an athlete can lose water and therefore weight with these techniques. There is a genetic element to this. Athletes who are heat adapted, i.e. acclimatized to hot environments, are likely to sweat more easily, as part of the adaptation to a hot environment are changes to increase the sweat response to more effectively cool the body.

The final thing that must be mentioned is that an athlete should aim to test their planned strategy, including replicating as many of the fight week training and activity conditions as possible, in advance to see how much weight they have the potential to lose and how ‘good’ they feel at the end of it. Of course, this is still no guarantee that the weight loss in the actual fight week will replicate this, and if the athlete will have unexpected health or performance outcomes. But it should at least highlight any obvious major red flags.

Rapid Weight Regain, Recovery and Performance

After the weigh in, athletes will attempt to rehydrate and restore glycogen before they start their fight. Evidence is mixed as to whether they typically achieve this … it seems likely it varies significantly between athletes depending on their knowledge of how to rehydrate and refuel, the time available between weigh in and competition to do this in, and the amount of water and glycogen they need to restore. It is also very hard to test whether an athlete is fully rehydrated and glycogen is restored (Barley et al., 2018). Easy to use hydration markers are equivocal, and very few athletes are going to be willing to give a muscle sample to test their glycogen levels just before they are about to go out and use those muscles on the competition floor!!

Is RWG aka rehydrating and refuelling important to performance? It seems logical that it would be. We know that carbohydrates are the primary fuel for high intensity performance and low carbohydrate availability increases fatigue and perception of effort. And moderate dehydration may adversely impact high intensity performance, concentration and grip strength. However, the results of studies are equivocal (Coswig et al., 2019). This might be because – as stated above – knowing if an athlete is effectively recovered from RWL is challenging. Plus, many other factors have the potential to impact performance making it a challenge to identify the impact of a single factor, as outlined in the introduction.

What are best practice considerations for recovery?

· Aiming to consume at least 1.5 x the volume of weight lost in fluids as not all take in will be absorbed. And aim to do this in a steady and regular fashion over the course of the recovery time i.e. don’t down it all in one go (Galloway, 1999).

· Including in the fluids a sodium concentration of 50-60mmol/l in the first 1-2 hours post weigh in to support recovery of salts (hydration = water + salts) (Galloway, 1999).

· Aiming to consume a rate of 10-12g carbs per kg of bodyweight per 24 hours, focussing on low fibre and fast digesting carbohydrates to maximise rate of digestion and absorption (and so anticipated refuelling) (Burke et al., 2011).

· Creatine supplementation of 20g soon after weigh in may also help accelerate carbohydrate reloading in the muscle, particularly if there is not time to eat as much carbohydrates as would be needed to restore muscle carbohydrate without creatine (Kreider et al., 2017).

If carbohydrates are drunk, e.g. in sports drinks, it is important to ensure the concentration of carbs is below 8-10%, i.e. 8-10g per 100g fluids (Burke et al., 2011). This is because any higher can slow gastric emptying and therefore digestion, and cause water to be drawn into the gut from the body, i.e. two things that will adversely impact refuelling and rehydration.

As with any competition nutrition strategy, the above should be tested in a trial RWL and RWG pre-fight. High carbohydrate intake, creatine, and significant fluid intake after dehydration can cause gut distress … and if this occurs food and drink is not going to be digested and absorbed effectively. Each athlete will have to test their limits, and also be willing to adapt on the day in the event their gut does not respond as expected.

Males vs. Females

Women are not small men, and men are not big women … and this can impact how each respond to weight cutting!

The short story is that the average woman is likely to drop less weight from equivalent water and carbohydrate cutting techniques than men. This means they might have to lose more weight in a fat loss phase prior to the weight cut to hit their desired weight class.

Women typically have lower muscle mass than men, which means lower glycogen (carbohydrate) stores and less glycogen associated water stores (Sims, 2015). So, depleting glycogen is going to result in less weight loss in women. More broadly, women typically have about 5% less total body water than the equivalent sized male thereby reducing the amount of weight that can be lost from water loss techniques. Women also tend to sweat less than males meaning more extreme temperatures and techniques may be required to induce significant sweat losses (Sims, 2015). And this carries with it increased risk of heat stress and related complications. Lower average sweat rates may be linked to the fact women have lower total body water.

On top of this, cutting water is likely to be more challenging when a female athlete is in the high hormone phase of the menstrual cycle, i.e. just before menstruation. The cumulative impact of high oestrogen and progesterone means women retain more water in their tissue and find it harder to sweat as blood volume drops (Sims, 2015). In addition, core temperature is higher and this may increase the risk of heat stress from sweat loss techniques.

You will notice that no specific values of how much less women may lose because of all these differences. This is because we simply don’t have the data to know, plus it will obviously differ between women dependent on factors from genetics, to body size, to training status, to heat acclimation.

It should also be noted that in many combat sports there are fewer female weight classes, which can mean some fighters must hold their weight lower and / or undertake a larger weight cut if they want to hit the lower weight class. The cost of this needs to be weighed up against any potential advantage of competing in the lower weight class.

Final Considerations

We still have much to understand around effective weight cutting. However, we do know that many athletes continue to engage in practices that are higher risk from a health and performance perspective. It could be because the ‘old ways’ are what athletes have always done and change is scary, particularly when your ability to participate in the fight is dependent on it. It could also be because the athletes’ nutrition outside of fight week is sub optimal … meaning they must engage in last minute large weight cuts. And it could also be because athletes tend to seek the advice of peers, coaches and social media over qualified nutritionists and other professionals (Connor and Egan 2019; Parks et al., 2019).

Changing the culture of weight cutting and broader nutrition will take time, and requires greater education, interaction and trust between athletes and qualified professionals. And the significant peer influence can be leverages, as there is the potential for a snowball effect from changing the practices of just a small proportion of athletes!

It is also important to emphasize that recommendations are likely to change over time as more research is performed and our understanding evolves. This is both to ensure athletes do not lose faith with apparently ever changing guidance, and so they remain alert for new guidance as it emerges.


Barley, O.R., Chapman, D.W., and Abbiss, C.R. (2019). The current state of weight-cutting in combat sports. Sports, 7, 123.

Barley, O.R. Iredale, F., Chapman, D.W., Hopper, A., and Abbiss, C.R. (2018). Repeat effort performance is reduced 24 hours after acute dehydration in mixed martial arts athletes. Journal of Strength and Conditioning Research, 32 (9), 2555-2561.

Burke, L.M., Hawley, J.A., Wong, S.H.S. and Jeukendrup, A.E. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29 (sup 1), S17-S27.

Connor, J., Shelley, A., and Egan, B. (2020). Comparison of hot water immersion at 37.8°c with or without salt for rapid weight loss in mixed martial arts athletes. Journal of Sports Science, 38 (6), 607-611.

Connor, J., and Egan, B. (2019). Prevalence, magnitude and methods of rapid weight loss reported by male mixed martial arts athletes in Ireland. Sports, 7, 206.

Coswig, V.S., Miarka, B., Pires, D.A., da Silva, L.M., Bartel, C., and Del Vecchio, F.B. (2019). Weight regain, but not weight loss, is related to success in real-life mixed martial arts competition. International Journal of Sport Nutrition and Exercise Metabolism, 29, 1-8.

Crighton, B., Close, G.L., and Morton, J.P. (2016). Alarm weight cutting behaviours in mixed martial arts: a cause for concern and a call for action. British Journal of Sports Medicine, 50 (8), 446-447.

Galloway, S.D. (1999). Dehydration, rehydration and exercise in the heat: rehydration strategies for athletic competition. Canadian Journal of Applied Physiology, 24 (2). 188-200.

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Matthews, J.J., and Nicholas, C. (2017). Extreme rapid weight loss and rapid weight gain observed in UK mixed martial athletes preparing for competition. International Journal of Sport Nutrition and Exercise Metabolism, 27 (2), 122-129.

Park, S., Alencar, M., Sassone, J., Madrigal, L., and Ede, A. (2019). Self-reported methods of weight cutting in professional mixed-martial artists: how much are they losing and who is advising them? Journal of the International Society of Sports Nutrition, 16, 52.

Reale, R., Slater, G., Cox, G.R., Dunican, I.C., and Burke, L.M. (2018). The effect of water loading on acute weight loss following fluid restriction in combat sports athletes. International Journal of Sport Nutrition and Exercise Metabolism, 28, 565-573.

Sims, S. (2015). In: ROAR. Roedale books, various pages.


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