A recent study by Oliver Barley et al. looked at how athletes in different sports cut weight and how much weight is typically cut in those sports. It found that weight-cutting in MMA focused more around dehydration than other sports, and that more weight was cut in MMA than in other combat sports.

The study looked at athletes participating in brazilian jiu-jitsu, boxing, judo, MMA, muay thai/kickboxing, taekwondo and wrestling. In total, 637 athletes completed a survey about their weight cutting habits.

Results

The mixed martial artists surveyed were the most extreme weight-cutters by any measure. The MMA athletes cut the most weight, both on their average cuts and their biggest-ever cuts. MMA athletes also lost more weight in the last 24 hours than any other class of athlete, both in absolute and relative terms.

MMA athletes gained around twice as much weight as most other sports between weigh-in and competition--though this result can be partially explained by the extra time between weigh-in and competition time MMA has compared to the other sports.

This tells us that athletes in MMA, even outside the very top level, are cutting more weight in shorter time periods than other athletes. Cutting weight in such short time periods basically always means dehydration techniques are being used, and the survey backs this assumption up. Wrestlers arguably developed and popularized the use of these techniques, but mixed martial artists used various methods of dehydration more often, even when compared to wrestlers.

63% of mixed martial artists lost weight by training in heated rooms. Only wrestlers (83%) did this more often.

76% of MMA athletes lost weight in a sauna. Only 51% of wrestlers used this method.

63% of MMA athletes lost weight by training in a rubber or plastic suit. Only wrestlers (83%) did this more often.

20% of MMA athletes spent a whole day in rubber/plastic suits. Only 17% of wrestlers used this method.

67% of MMA athletes used “water loading” as part of their weight-cutting process. Only 53% of wrestlers did the same thing.

There are some extreme methods of cutting weight that mixed martial artists are less likely to use than other athletes, though. MMA athletes were less likely to report using diuretics, laxatives or vomiting to lose weight compared to most other surveyed combat sports.

Weaknesses

This study relies on self-reported information about both the amount of weight cut and the methods used. Self-reporting information about weight can be unreliable, but in theory, this should apply to all sports, the comparison from sport to sport shouldn’t be significantly affected.

There may also be cultural differences between sports that makes reporting the use of specific methods more or less likely.

The study doesn’t examine the cutting of water weight in depth, which typically takes place in the few days before a weigh-in. Instead, the survey jumps from two weeks to 24 hours, making it less useful for examining exactly how much of each sports’ weight loss is caused by acute dehydration.

Some common methods of cutting weight, such as hot baths and towel-wrapping, aren’t included, again making the study imperfect for examining the methods of weight-cutting in MMA.

The study uses a slightly modified version of a longstanding and well-accepted survey originally used to look at the weight loss methods of judo athletes. Some of the identified weaknesses are likely caused by the understandable decision to use this study rather than try to design a new survey which wouldn’t be backed by the same historical evidence of effectiveness.

What this study tells us

The primary takeaway from this study is the confirmation that athletes in MMA cut more--often significantly more--weight than other combat sports athletes. This isn’t a huge surprise, as data from California shows around half of elite mixed martial artists are cutting around 10% of their body weight on fight week, an amount considered “severe” dehydration, which requires medical care.

This study highlights how MMA has a uniquely large problem with weight-cutting in terms of both the amount of weight being cut and the prevalence of weight-cutting at all levels of the sport. Severe dehydration due to weight-cutting could be having chronic health effects on athletes, to say nothing of the acute risks, like death.

The California State Athletic Commission (CSAC) has introduced policies to reduce the most dangerous weight cuts, and the Mohegan Sun and Brazilian commissions (CABMMA) have recently decided to adopt the same rules. This study shows that the practice of severe dehydration to make weight happens worldwide, and more regulating bodies need to make the decision to combat this issue sooner rather than later.