What is metabolism really? Statements like “he can eat a lot because he has a fast metabolism” are somewhat misleading.
新陈代谢是什么？“他很能吃是因为他新陈代谢很快”像这样的说法有点误导我们。
Metabolism isn’t about the digestion of food in your stomach; it’s the name given to all of the chemical changes that occur in an organism’s tissue cells. There are basically two kinds of chemical changes that can occur; tissue matter can be built, or it can be broken down.
新陈代谢不是指食物的消化能力，而是指一种在组织细胞内发生的化学变化。基本上可分为两类化学反应：合成或分解组织细胞。
These processes are called anabolism and catabolism. More specifically, anabolism is responsible for an organism’s growth, its maintenance, and the repair of its tissues. So when you cut yourself and your skin scabs over and heals, you’re seeing anabolism at work. Or if you grow taller or wider, that’s also evidence of anabolism.
这些过程叫作合成代谢和分解代谢。具体地说，合成代谢负责有机组织的数量增长，维护和修复。所以，当皮肤割伤后会自动结疤愈合，这就是合成代谢在起作用。或者长高长胖，那也是合成代谢。

In order to build tissue and repair it, however, anabolism requires energy, as well as material with which to build. This energy and building material comes from the breaking down of larger, more complex material, a process called catabolism. As well as producing energy and building material, catabolism also breaks down material for excretion from the body.
要建造和修复组织细胞，合成代谢需要能量和原料。而能量和原料就来自于分解更大，更复杂的细胞，这个过程就叫分解代谢。与合成反应一样，分解代谢需要的能量和原料来自于身体的分泌物。
Both anabolism and catabolism are necessary for survival and good health. Understanding these processes can help one make good decisions about exercise and diet. For example, when an athlete trains, her muscle fibers break down. However, the daily recommended amount of protein is all that is needed to meet the anabolic and catabolic needs of the body and thus repair muscles fibers.
合成和分解代谢在对于身体健康很重要。而了解这些过程可以帮助我们对运动和饮食做出更好的决定。例如，运动员训练时他的肌纤维会受损。所以每日推荐的蛋白质就是身体合成和分解代谢所需的量，这样才能修复肌纤维。