Extreme weight cuts are arguably the worst enemy of every fighters career longevity and health, however, they still keep on doing it.
Some fighters like Khabib Nurmagomedov, Conor McGregor, Anthony Johnson etc. have claimed that they have cut 20 pounds in the week ahead of the fight. Not only the drastic decrease of their bodyweight is harmful for them, the sudden weight gain that comes the day after that is also taxing.
It is true, that you wouldnt know how it feels, until you experience it, but we do not encourage anyone to try it. Nevertheless, you can get a taste of it just by looking at these UFC fighters at their weigh-ins: