Combat sports like wrestling, boxing and judo are always fought in various weight categories and athletes are bound to be always under the said weight of the respective class they are competing in. For example, Vinesh was fighting in 50kg and she has to be below 50kg.
To determine this, there’s weigh-in.
In the case of wrestling at the Olympic Games, weigh-ins are organised each morning of the concerned weight-category. Since competitions are stretched over two days in wrestling with the repechage and medal rounds scheduled on the second day, there are two weigh-ins. The weigh-in time limit for a wrestler on the first day is 30 minutes while it’s 15 minutes on the second day.
Importantly, contestants must be in perfect physical condition, with their fingernails cut very short, for the weigh-in.
Throughout the entire weigh-in period, wrestlers have the right, each in turn, to get on the scale as many times as they wish.
Say a wrestler competing in 50kg category is 50.2kg on the opening day, then he/she can do calorie-burning activities like running or skipping or even a small stint in the sauna that help them lose water in their body through sweat and hence weight to go under the requirements.
Some even choose to cut their hair in case they are a few grams over.
For each his own actually. Since it’s no-brainer that consumption of food leads to weight gain, wrestlers are extremely aware of what they eat or drink.
As the sport is extremely demanding with them requiring to fight multiple bouts on a single day and then one or two more on the second day of competition if they advance directly or through repechage, the wrestlers learn to manage it but in a brutal way.
While they hydrate themselves during the day to keep themselves fit, many don’t even drink even a sip of water throughout the night before the weigh-ins. In most cases it’s night of intense running, skipping, sauna and starving.
Basically sucking as much water out from the body as possible. The human body is made up of 60 percent of water and that’s what they target.
Wrestlers usually participate in a weight category less than their natural weight and that was the case with Vinesh who lowered herself from 53kg class to 50kg for the Paris Olympics.
While she did an excellent job in maintaining it for the opening weigh-in, three bouts in a single day where she had to eat/drink to stay fit meant she was going to gain pounds.
Vinesh ended up gaining 1.5kg following her bouts on Tuesday and then put her body through a wringer in a bid to lose all of it. She spent the entire night alternating between running and sauna but the task proved too insurmountable and was found 100 grams overweight. She even cut her hair but to no effect.
Also, according to many coaches, it’s far harder for women to lose weight than men as they have much lesser water content.