人们已认识到维持生命必须的食物主要有三种类型。第一种是碳水化合物，这些碳水化合物广泛存在于动、植物，包括糖、淀粉及纤维分子，为人体提供能量。碳水化合物还能合成
生物过程所必须的葡萄糖酶。第二种是脂肪。脂肪是比碳水化合物更为“浓缩”的食物能量，但是，它只作为贮存能而不是立即可用的能量。第三种是蛋白质。蛋白质是由含碳、氢、氧和氨元素的大分子组成的。蛋白质主要不是用于提供能量，而是组成生命所必需的结构物质。
It is known to maintain life must food mainly have three types. The first is a carbohydrate, these carbs exist widely in plants and animals, including sugar, starch and fiber molecules, provide the energy for the human body. Carbohydrate also can synthesize biological process must the glucose enzymes. The second is adipose. Fat is more than carbohydrates "enrichment" food energy, but it only as storage can not immediately available energy. The third one is protein. Proteins are made up of carbon, hydrogen, oxygen and nitrogen element composed of macromolecules. Proteins are not mainly used to provide energy, but components necessary to life structure material.