減重對一般人而言，是爲了健康及美觀，可是對有運動級別的運動選手，就要特別注重體重的控制，不僅僅是爲了健康及美觀，還要爲了其比賽級別的選擇及運動成績的表現。運動選手常常在平時練習的時候，就忽略體重增減的重要，往往到了比賽爲了選擇比較好得名次的級別，或者是爲了避開強勁的對手，而以增加體重或降低體重，以選擇對自己更有利的比賽賽程及對手。增加體重以提升運動選手比賽的級別，似乎對其運動表現不會產生重大的影響，而且也比較容易達成增加體重的目標。可是，對降低體重，以調降運動選手的比賽級別，相對也比較不容易，而且降低體重對生理影響也比較大。是否這樣的結果，會影響到運動選手，在運動成績上的表現？再者，要如何降低體重？其降低的速度要如何？其原理可以應用到有運動級別區分的運動選手。

General speaking, the purpose of weight-reduced is focus on the heath and figure of body. However, Not only for health and beauty but also are athletes focus on their performance of exercise. In general, athletes do not pay much attention to their weight-controlled in off season. When the regular season is coming up, they are worried about their weight-controlled since they are over weight. In this case, subjects have to reduce their weight to qualify their weight measurement before the competition. For athletes, the purpose of weight-reduced is to choose the matches which are easy to get ahead or to defend their championship. To reduce their weight in a short period of time, it is whether good or bad to their health and their performance on exercise competition or not. It is the point of the discussion and, also, it can be applied to other exercise competitions, which are divided to several grades.