Research · Combat Sports Safety

Weight Cutting in Combat Sports: What the Research Says About the Risks — and What Actually Works

By Muhammad Dzulhisham · MSc Sports Coaching, NSCA-CSCS

Every combat sport that uses weight classes exists on the same uneasy compromise: divide athletes by mass to keep bouts fair, then weigh them in hours or days before they actually compete. That gap between the scale and the fight is where "weight cutting" lives — and it has quietly become one of the most normalized dangerous practices in youth and adult sport. A 2024 systematic review in Nutrients found that some form of pre-competition weight loss occurs in 66 to 100 percent of combat athletes studied across fourteen disciplines, from judo and taekwondo to boxing, wrestling, and mixed martial arts.¹ Most of that weight is not fat. It is water, glycogen, and gut content, stripped off in the final one to seven days through methods that range from sensible to lethal.

This is not a fringe issue confined to elite professionals making six-figure paydays. It is a practice that starts, according to the research, remarkably young.

The physiology of a cut, and why it goes wrong

Rapid weight loss (RWL) protocols typically combine restricted fluid and food intake with active dehydration — sauna sessions, hot baths, plastic or rubber "sweat suits," and exercising in overheated rooms. The goal is to lose several percent of body mass as fluid, make weight at the official weigh-in, then rehydrate and refeed before stepping onto the mat or into the cage. The Nutrients review noted that the most common methods are simply increasing exercise and gradually restricting diet, but a meaningful minority of athletes escalate to fasting, vomiting, laxatives, and diuretics when a cut is not going to plan — and that coaches, not doctors or sports scientists, are overwhelmingly the ones directing these decisions.¹

The danger is that the body does not treat 5 to 8 percent acute fluid loss as a cosmetic adjustment. Plasma volume drops, cardiac stroke volume falls, thermoregulation is impaired, and the kidneys are placed under acute stress at exactly the moment an athlete is also training or competing. The American College of Sports Medicine's original 1996 position stand on the subject, prompted by decades of wrestling-specific concern, documented that rapid weight loss among high school and collegiate wrestlers averaged roughly 2 kilograms a week and could exceed 2.7 kilograms in a fifth of wrestlers — with a third of high schoolers repeating the cycle more than ten times across a single season.²

When the cut goes too far

The reason sports medicine bodies treat this as urgent rather than theoretical is that the pattern has killed people. In late 1997, three American collegiate wrestlers — Billy Jack Saylor, Jeff Reese, and Joseph LaRosa — died within a 33-day span while attempting rapid weight loss, in Reese's case from kidney and heart failure brought on by dehydration and extreme exercise. The deaths triggered an NCAA investigation and, within months, a sweeping set of rule changes: saunas, rubber suits, and diuretics were banned outright, training-room temperatures were capped, weigh-ins were moved to within one to two hours of competition instead of the day before, and a mandatory hydration and body-composition certification program was introduced for every wrestler.³

The pattern has not stayed confined to wrestling, and it has not stayed confined to adults. In November 2017, 18-year-old Jessica Lindsay collapsed in Perth, Australia, while attempting to cut roughly 17 pounds in seven days for an amateur Muay Thai bout, following a training regimen of sauna sessions, hot salt baths, sweat-suit running, and a diet of plain rice. She died four days later; the coronial inquest found the cause to be multiple organ failure from the combined effects of hyperthermia and dehydration.⁴ In mixed martial arts, Brazilian fighter Leandro Souza died in September 2013 after using diuretics to make weight for a regional card, and ONE Championship flyweight Yang Jian Bing died in 2015 of cardiopulmonary failure following severe dehydration from a weight cut. An academic analysis of the practice noted that one study of 40 MMA fighters found 39 percent were significantly or seriously dehydrated 22 hours after weigh-in — despite the body typically needing up to three days to fully rehydrate.⁵

A weight class exists to protect the athlete on the other side of the mat — not to reward whoever can dehydrate the fastest.

Why adolescent athletes are not just smaller versions of adults

The case for treating this as a distinct youth-safety issue, rather than a professional-sport curiosity, comes from a 2022 systematic review in the Journal of Eating Disorders that pooled data from over 3,100 young combat athletes across wrestling, judo, and boxing.⁶ Its findings are sobering for anyone coaching junior athletes:

• Rapid weight loss prevalence in youth ranged from roughly 25 to 80 percent depending on sport and level, and some athletes reported beginning weight-cutting behavior as early as ages four to nine.
• Energy restriction timed to fall during critical growth windows carries a documented risk of delayed puberty and impaired growth and hormonal maturation — precisely the phase of development youth sport is supposed to protect, not compromise.
• Two adolescent girls in the pooled data experienced amenorrhea lasting more than a year, a marker of the kind of energy-availability disruption seen across other weight-restricted youth sports.
• Disordered eating patterns were common: up to 52 percent of the wrestlers surveyed reported binge-eating behavior, and 1.7 percent met clinical criteria for bulimia nervosa.
• Documented psychological effects of the cutting-and-rebound cycle included measurable increases in depression, anger, and fatigue in the days surrounding weigh-in.

The mechanism behind several of these findings is not exotic: an adolescent body diverts limited energy toward whichever systems are under the most immediate pressure. When that pressure is an artificial, coach-driven deadline to make a number on a scale, growth, reproductive endocrine function, and mental health are what get deprioritized. None of this requires a fighter to die for it to count as a health cost — it is a slower, quieter toll that a single "successful" weight cut can mask entirely.

What the governing bodies actually recommend

Sports medicine's response has been to replace vague warnings with specific, testable rules. The ACSM revisited and formally replaced its 1996 position stand in 2021 with an Expert Consensus Statement covering weight-category sports broadly, not just wrestling. Its core strategies are: set each athlete's minimum competitive weight class from a preseason body-composition assessment rather than a coach's guess, shorten the window between weigh-in and competition so there is less time to exploit with a rebound, and explicitly prohibit unhealthy weight-making techniques such as saunas, rubber suits, diuretics, and laxatives.⁷

The most recent applied guidance, a 2025 International Society of Sports Nutrition position stand on combat sports weight-cutting, goes further by putting numbers on what "gradual" should mean in practice: during an 8-to-10-week fight camp, body mass reduction should track around 0.5 to 1 kilogram per week to protect lean tissue and performance, with any acute pre-weigh-in cut kept as small as the calendar allows — the statement flags 6.7 percent of body mass as an outer ceiling at 72 hours out, tightening to 4.4 percent inside 24 hours. It also lays out a structured rehydration and refeeding protocol for the period after weigh-in: oral rehydration solution first, moderate carbohydrate intake following, and a target of regaining at least 10 percent of body mass before competing. Notably, the statement is explicit that fasting, diet pills, enemas, laxatives, and purging are not endorsed under any circumstance, and it flags the long-term health effects of repeated cutting cycles as still not well understood — an honest admission that the science here is still catching up to the practice.⁸

The National Athletic Trainers' Association's 2011 position statement takes a similar line aimed specifically at the people closest to young athletes — coaches and parents — recommending education on the dangers of fasting and dehydration, discouraging any practice that manipulates hydration status to make weight, and calling for medically supervised, individualized weight and body-composition targets rather than one-size-fits-all cutting culture.⁹

Safer alternatives that are already working

None of this is purely theoretical guidance sitting in a journal. American scholastic wrestling — the sport that prompted the 1996 ACSM stand in the first place — now runs mandatory minimum-weight certification programs built directly on this research. A typical current program requires a hydration check (urine specific gravity capped at 1.025), a body-composition assessment that sets a floor of roughly 7 percent body fat for male athletes and 12 percent for female athletes, and a rule that weekly weight descent may not exceed 1.5 percent of body mass — with a small built-in growth allowance added mid-season so that a normally growing teenager is not penalized for gaining weight the way a body is supposed to.¹⁰

The professional side of combat sports has produced its own version of the same idea, and it happens to be headquartered in Singapore. In 2017, ONE Championship became the first major MMA promotion to formally ban dehydration-based weight cutting, replacing the old day-before weigh-in with a "walking weight" system: fighters are tested for hydration status on arrival for fight week and again on fight day itself, must sit within their weight class throughout, and compete close to their natural body mass rather than rehydrating a large deficit overnight. Weight classes were also widened to reduce the incentive to cut in the first place.¹¹ It is a live, large-scale demonstration that a major combat sports organization can remove the most dangerous piece of the tradition without removing the sport's competitive structure.

For athletes and parents outside of a governed federation — the amateur Muay Thai, boxing, and grappling scene that makes up much of Singapore's combat sports community, where no equivalent hydration-testing mandate exists — the practical takeaway from this research is the same one the guidelines converge on: body composition should be managed across months of training, not days. That means setting weight targets from an actual body-composition assessment rather than an arbitrary number, building in a genuine off-season and pre-camp runway of 8 to 10 weeks for any meaningful mass change, preserving protein intake through a cut to protect muscle and connective tissue, and treating fluid restriction, sauna use, and fasting as red flags rather than routine tools — especially for any athlete who has not yet finished growing.

The bottom line

Weight classes are a genuine safety mechanism in combat sports — they exist so a 55kg athlete does not have to face someone who walks around at 75kg. The tragedy of dehydration-based cutting is that it quietly defeats the very purpose of the weight class it is used to game, while exposing the athlete doing the cutting to real, occasionally fatal, cardiovascular and renal risk. For adolescent athletes still going through growth and puberty, the research adds a second layer of concern that has nothing to do with a single dangerous weekend: chronic, repeated energy restriction timed around a competitive calendar can quietly interfere with the growth and hormonal development that youth sport is meant to support. The consistent message from ACSM, NATA, and the ISSN is not "don't manage weight" — it is that weight management done slowly, individually, and with real body-composition data behind it protects both the athlete and the sport, while a scale number gamed at the last minute protects neither.