What is metabolism really?
新陈代谢是什么？
Statements like “he can eat a lotbecause he has a fast metabolism” are somewhat misleading.
“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;
新陈代谢不是指食物的消化能力，
it's the name given to all of the chemical changes that occur in an organism's tissue cells.
而是指一种在组织细胞内发生的化学变化。
There are basically two kinds of chemical changes that can occur; tissue matter can be built,or it can be broken down.
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.
这些过程叫作合成代谢和分解代谢。
More specifically, anabolism is responsiblefor an organism's growth, its maintenance, and the repair of its tissues.
具体地说，合成代谢负责有机组织的数量增长，维护和修复。
So when you cut yourself and your skin scabs over and heals, you're seeing anabolism at work.
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。
Or if you grow taller or wider, that's also evidence of anabolism.
要建造和修复组织细胞，合成代谢需要能量和原料。
In order to build tissue and repair it, however, anabolism requires energy, as well as material with which to build.
或者长高长胖，那也是合成代谢。
This energy and building material comes from the breaking down of larger, morecomplex material, a process called catabolism.
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。
As well as producing energy and building material,catabolism also breaks down material for excretion from the body.
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.
合成和分解代谢在对于身体健康很重要。
Understanding theseprocesses can help one make good decisions about exercise and diet.
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。
For example, when anathlete trains, her muscle fibers break down.
例如，运动员训练时他的肌纤维会受损。
However, the daily recommended amount of proteinis all that is needed to meet the anabolic and catabolic needs of the body and thus repair musclesfibers.
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。
