Martial arts nutrition: making weight, energy and competition

Why does dehydrating yourself to make weight hurt performance?

Rapid weight cutting means losing several kilos in a few days using saunas, plastic wrap, very little water or diuretics. It harms performance and puts health at risk. A review of studies in combat sports measured these effects [2]. When rapid loss reaches 5% of body weight or more, fatigue increases and mood, strength and power worsen [2].

Even a smaller loss can matter. Losing more than 2–3% of body weight through dehydration already impairs performance, according to joint sports nutrition guidance from the United States and Canada [1].

Your kidneys are affected too. A 2021 review found markers of acute kidney injury in most studies of combat athletes who dehydrated themselves to make weight [3]. Restricting water reduces blood volume. The heart has to work harder, and regulating body temperature becomes more difficult.

A dehydrated athlete steps onto the tatami more tired and in a worse mood, just when quick decisions matter.

How to reach your weight class without losing strength

The safe way to reach your weight class is to lose weight gradually, allowing weeks or months [2]. The aim is to lose fat while preserving muscle, which provides power for strikes and throws. The WHO recommends strength training on two or more days a week. This helps preserve muscle.

To protect muscle, 1.4 to 2.0 g of protein per kilogram of body weight per day is recommended, spread every three to four hours [4]. The amount may be higher during an energy deficit [4]. For someone weighing 70 kg, that is 98 to 140 g a day. If you have kidney disease, your nephrologist or dietitian can advise how much protein, potassium, phosphorus and other minerals and electrolytes are right for your stage.

For carbohydrates, joint US and Canadian sports nutrition guidance recommends 5 to 7 g per kilogram per day with an hour of training daily [1]. With one to three hours of intense activity, this rises to 6–10 g [1]. Fat should provide 20% to 35% of energy, and should not fall below 20% [1].

If you want to gain muscle while competing close to your natural weight, see our fitness diet for muscle gain. If you compete in judo, our judo nutrition guide covers its weigh-in in detail.

What to eat and drink on weigh-in day

The weigh-in schedule is set by each federation’s rules and changes your strategy, so check it before planning. In 2017, a review by the Australian Institute of Sport reported that judo, wrestling and taekwondo weighed athletes the afternoon before [5]. In boxing, weigh-ins took place on the same morning, three to twelve hours before the bout [5].

The same review reports that more than 80% of athletes weighed the day before arrived to compete dehydrated, as did more than 95% of those weighed in the morning [5]. The safest approach is to arrive at weigh-in hydrated and close to your natural weight.

If you weigh in the day before and have lost some weight, drink 1.25 to 1.5 litres for every kilogram lost [1]. Have sodium and carbohydrates with it; they help your body retain water [1].

If weigh-in is only a few hours before, there is no time to recover from dehydration. It makes sense to compete close to your natural weight. Eating low-fibre foods in the days beforehand reduces gut contents, although no study has measured how much weight this loses [5].

What to eat before stepping onto the tatami or into the ring

Your pre-competition meal replenishes muscle energy stores without weighing on your stomach. The recommendation is 1 to 4 g of carbohydrate per kilogram of body weight between one and four hours before competing [1].

Keep the meal low in fat, moderate in protein and low in fibre so your stomach can empty beforehand [1]. A turkey sandwich or a ripe banana can also work when time is short.

To hydrate, drink 5 to 10 ml per kilogram in the two to four hours beforehand [1]. At 70 kg, that is 350 to 700 ml, or two to three large glasses.

Between rounds and bouts: how to replenish energy

In a tournament with elimination rounds, what you eat and drink between bouts affects how much strength you have left for the final. During short breaks, start by replacing fluids and simple sugars.

For efforts lasting one to two and a half hours, the recommendation is 30 to 60 g of carbohydrate per hour [1]. In a tournament with short bouts and long waits, this means small, regular servings. Sipping a sports drink with water, carbohydrates and sodium helps you maintain your pace without bloating.

With two or three hours between rounds, choose a ripe fruit, dried fruit or a low-fat cereal bar. The same approach applies to other intermittent sports, such as in our basketball nutrition guide.

What to eat after competing to recover

After a bout or a hard training session, rehydrate, repair muscle after the impact and replenish the glycogen you have used.

For fluids, use the same guideline of 1.25 to 1.5 litres per kilogram lost [1]. To support muscle recovery, each serving should contain about 0.25 g of protein per kilogram, or 20 to 40 g [4].

If you compete again in less than eight hours, the recommendation is 1 to 1.2 g of carbohydrate per kilogram per hour for the first four hours [1]. A white-bread turkey sandwich and a milk-and-banana smoothie cover the first serving.

What happens if your weight goes up and down for every tournament?

Restricting food before weigh-in and then eating without control afterwards, tournament after tournament, can harm your health in the medium and long term.

The International Olympic Committee describes this as Relative Energy Deficiency in Sport (REDs). Eating less than you use over a long period damages bone, weakens immunity, disrupts periods and lowers your resting metabolic rate [6]. The same consensus identifies weight-class sports as among those at greatest risk of eating disorders [6].

If the scales make you anxious, you skip meals to compensate or eat in secret after weigh-in, ask for help. A psychologist specialising in eating behaviours can assess the situation.

Fat-loss supplements have little or no effect [7]. Any supplement may also contain undeclared prohibited substances, including stimulants and diuretics [7]. Diuretics are prohibited in competition [5]. If you need a supplement for another reason, it should be prescribed by your doctor or dietitian.

What mistakes do we see in consultations?

• Leaving weight loss until the final week. What has not been lost over a month ends up being lost as water, and dehydration impairs performance in a bout.
• Cutting out bread, pasta and rice to make weight. You lose glycogen and water, and your strength and technical training suffer.
• Moving down a weight class because the opponents above seem stronger. If every tournament requires a week in the sauna, that class is not a good fit for your body.
• Drinking too little during a tournament because you do not feel thirsty. You can lose more fluid between bouts than you realise.