The idea behind cutting weight before a fight stems from the concept that you want to be the biggest and strongest within the weight class at which you fight. So theoretically the fact that you have done so will give you an advantage over your opponent. Given that skill, technique, and will are about equal the fight will be won by the bigger stronger fighter.
The perfect example of why you would cut weight for a fight
If you want a real life example that will blow your mind look no further than UFC fighter Rich Franklin. I’ve heard that the dude walks around at 215 lbs and having spent a majority of his career at middleweight that would mean he cut 30 lbs to make weight. Which in turn made him bigger and stronger than a large portion of his opponents. He dominated the UFC middleweight division (at least until he ran into Anderson Silva) proving that there’s obviously something to manipulating your weight before a fight.
How to cut weight
There are four main ways to cut weight for your fight:
Click on the links above to read about each way to cut weight for your fight.