How to make your judo weight class smartly instead of weakening yourself with a crash diet: safe limits, recovery time and why less is often more.
The honest answer first: most judoka make too much weight — and the science clearly advises against it. Rapid weight loss (RWL in the jargon) is extremely common in judo: depending on the study, 40 to 93 % of judoka do it, typically around 5 % of body mass — for 80 kg that's about 4 kg, often in a few days. The catch: the benefit is smaller and the risk bigger than most think.
The key finding is actually reassuring: a weight loss brings no performance drop — as long as you have more than 4 hours to recover and refill after the weigh-in. With less time, performance sags. And long-term, the constant up and down is linked to a higher injury risk. That's why the most honest recommendation of the reviews is simply: avoid RWL where possible.
Straight talk: you fight better fed and strong than starved one class lower.
The most important lever happens before any diet: the class choice. In the off-season, stay within around 12–15 % over the class limit — whoever floats 25 % above their "dream class" day-to-day suffers every single time. The best diet is the one you don't need at all.
Reduce over weeks, not over nights. As rough upper limits for a safe reduction, count around 6.7 % of body mass over 72 hours, 5.7 % over 48 hours and 4.4 % over 24 hours — the tighter the time, the less you should want to drop at all.
Even while making weight, the tank must not run empty. As floors, the ISSN position stand names 3–4 g carbs, 1.2–2.0 g protein and 0.5–1.0 g fat per kg of body weight. Protein protects your muscles, carbs your explosiveness — you need both on the mat.
This is where it all decides: after the weigh-in you refill deliberately — fluid, electrolytes, carbs. The recommendation: regain at least 10 % of body mass before the match. And because from 4 hours of recovery no performance drop is measurable, this refill window is your most important tool.
Acute dehydration via sauna and sweat suit (2–4 % body mass) belongs exclusively under professional supervision — alone and overdone, it's dangerous. For recreational and amateur judoka it's simply not necessary.
Making weight is about more than performance — it's about health. Constant weight cycling, the repeated up and down, is linked to an increased injury risk, and the long-term effects of frequent crash cures are simply not sufficiently researched. For youths and beginners the rule is therefore: no RWL. Acute water manoeuvres (sauna, sweating, fluid stops) never alone and never to the extreme — dehydration hits circulation, focus and reaction time, exactly what keeps you safe on the mat. When in doubt: fight one class up and stay healthy.
Keep a simple weight log over a normal month before you even think about a class: weigh in the morning after getting up, note it down. After four weeks you know your real everyday weight and its swing — and you pick the class that needs only a few hundred grams of clean fine-tuning instead of a week of starving. The strongest judoka are rarely the ones who lose the most weight, but the ones who have to lose the least. You make weight in your head and your calendar, not in the sauna.
As rough upper limits, count around 6.7 % of body mass over 72 hours, 5.7 % over 48 hours and 4.4 % over 24 hours. The less time, the less you should reduce at all. More important than any number: early and slow instead of a crash in the last days.
Not necessarily — the recovery time is decisive. If you have more than 4 hours to refill after the weigh-in, no performance drop is measurable; with less time performance falls. That's why deliberate refilling after the weigh-in (at least 10 % back) is so important.
It's common (40–93 % of judoka), but not harmless: constant weight cycling is linked to more injuries, and the long-term effects are insufficiently researched. The science recommends avoiding RWL where possible — especially for youths and beginners.
Even in a deficit you hold floors: around 3–4 g carbs, 1.2–2.0 g protein and 0.5–1.0 g fat per kg of body weight. Protein protects the muscles, carbs the explosiveness. An empty tank costs you exactly the power you're making weight for in the first place.
Judo: Understanding Competition — Ippon, Waza-ari, Rules