Judo is an event with weight classes. Many athletes believe that rapid weight loss can give them advantages to compete against smaller opponents. Thus, rapid weight loss is very prevalent among Judo athletes. Most of the rapid weight loss methods involve restricted fluid intake, restricted diet or dehydration, which is extremely harmful to health, and may result in negative effects on muscular strength and endurance. However, because the negative effects of rapid weight loss can be reversed within several hours, many athletes are still willing to conduct rapid weight loss even with high healthy risks. This situation should be corrected by setting up regulations.