Almost everyone considers going on a diet sometime in his or her life. All, regardless of sex and age, have something in common - losing weight and losing it fast.

Though their common aim may seem basically good, they probably do not realize that misguided dieting can do more harm than good to their health. Going on too strict a diet can destroy the balance of chemicals in the human body. This happens because when the body is suddenly given much less food than usual, it feels as though it is being attacked and tries hard to protect itself by saving energy. It does this by slowing down metabolism, the process by which the food we eat is converted into energy. As energy is supplied to the body at a slower and slower rate, dieters gradually become so weak that they can do nothing. They soon lose interest in everything going on about them, and their resistance to illness becomes so low that they are easily attacked by one illness after another.

Most of those who diet know that foods like rice, bread, potatoes, cakes, sweets, fruits and some vegetables contain carbohydrates, and so can make one fat. What they do not realize, however, is that carbohydrates are our bodies' main source of energy, and that these foods also contain components essential for the composition of substances that are needed to keep the body healthy. As a result, they try to avoid eating these foods, and consequently, they become weaker and less healthy. They begin to have difficulty sleeping properly and start to suffer from radical mood changes. In more serious cases, they even begin to show signs of mental illness.

It is strange enough that most strict diets recommend artificial sweeteners to take the place of sugar and other natural sweeteners. In fact, such artificial sweeteners actually increase one's appetite and lead to one's eating even more than usual.

Of course, the fact that misguided forms of dieting result in so many problems does not mean that no dieting is safe or all dieting is harmful to the health. Proper dieting can not only help a person lose ugly excess fat, but can also help him or her to keep it off and to lead a more active, happier and healthier life.

You might ask just what a proper diet is. Well, simply expressed, a proper healthy diet is one that is well-balanced, or, in other words, one that includes enough but not too many of the kinds of foods that provide the body with the nutrients that it needs to function properly. The most important of these nutrients are the macronutrients: proteins, carbohydrates and fats. The body needs fairly large amounts of proteins and carbohydrates for building material and energy. Meat, fish, eggs, milk, cream, and nuts all contain proteins and foods like rice, bread, potatoes, etc. Contain carbohydrates. The body needs fat to keep it from the cold and to provide a protective layer for the organs, but only in small quantities.

Vitamins and minerals such as iron, calcium, are another group of essential nutrients, though the body does not need as great a quantity of these as it does the macronutrients - proteins, carbohydrates and fats.

There are two types of vitamins, water-soluble vitamins and fat-soluble vitamins. Water-soluble vitamins like vitamin C and the B-group vitamins do not stay in the body long and so foods containing these vitamins need to be taken rather often. On the other hand, the fat-soluble vitamins, vitamins A, D, E and K stay in the body for long periods of time and so there is no need to take foods containing them so often.

One way of getting enough nutrients while keeping one's weight down is to take substitutes for foods which contain too much fat. For example, instead of regular milk, one can take skimmed milk, which contains as many proteins and minerals as regular milk but has had the fat removed. In the same way, vegetable oil can be used for cooking instead of animal oil.

几乎每一个人在他或她的一生中都有个时候考虑要节食。所有的人，不分性别和年龄，都有个共同之处--要减轻体重，而且要快速减肥。

尽管他们共同的愿望令人觉得好像基本上是好的，但是他们也许并没意识到，用这些误导的节食方法，对他们的身体健康来说害大于利。过于严苛地节食会破坏人身体内生物化学结构的平衡。之所以会产生这种结果，是因为当人身体突然得到的食物比平时少了许多的时候，身体就会觉得好像受到了袭击，于是身体就用节约能源支出的办法尽量设法来保护自己。我们的身体通过减慢新陈代谢速度的办法来保护自己，亦即减慢把我们所吃的食物转化成能量的过程。由于以越来越慢的速度给身体供应能源，这些节食的人的身体就逐渐变得非常虚弱，以致弱到什么事都不能做的程度。于是这些节食者很快就会对他们周围所发生的一切事情都失去了兴趣，结果他们的身体对疾病的抵抗能力就变得非常低，以致于他们很容易地就会受到一种又一种疾病的连续袭击。

绝大多数节食者都知道，像大米、面包、土豆、蛋糕、糖果、各种水果和一些蔬菜等各类食品都含有碳水化合物（即淀粉），因而，都会使人发胖。可是，他们都没意识到碳水化合物是我们身体的主要的能源，他们都没意识到这些食品里都含有使我们的身体健康所需要的一些物质的基本成分。结果，他们尽量避免吃类食品，因而他们的身体就变得越来越虚弱、越来越不健康。他们开始有了不能适当睡眠的难题、开始产生了思想情绪上的一些根本变化。在一些较严重的病例中，病者甚至开始显露出有精神病的一些征兆。

说来也真奇怪，那些最严格的节食的食谱推荐用人造的甜味剂来代替蔗糖和其他天然的甜食品。事实上，这类人造的甜味剂实质上增大了一个人的食欲，结果反而使人比平时吃得更多。

当然，种种错误的节食方法导致了很多问题，但这些事实并不意味着没有任何一种节食的方法是安全的，也不意味着一切节食方法都对健康有害。恰如其分地节食不但能帮助一个人去掉难看的多余脂肪，而且能帮助一个人把节食的成果保持下去，能帮助一个人过上一种更加充满了青春活力的、更为愉快的、更为健康的生活。

你很可能会问，到底什么样的节食食谱才是恰如其分的。噢，简单地讲，有益于健康的节食食谱，就是各种食物都能很好地均衡的食谱。换句话说，就是这种节食食谱中包括了足够的各种食品，但都不要吃得过多。这足够的食物足可以提供给我们的身体在适当地发挥其功能时所需要的各类营养物质。这些营养物质中最重要的就是人体所需的 大量的营养物质：各类蛋白质、碳水化合物、各类脂肪。人的身体需要有相当量的蛋白质和碳水化合物作为各器官的建筑材料和人活动的能源。肉、鱼、蛋、奶、奶油和各种坚果里面都含有蛋白质，像大米、面包、土豆之类的食品里都含有碳水化合物。人体为了御寒需要脂肪，脂肪能为各种器官提供保护层，但仅有少量的脂肪也就足够了。

各种维他命（维生素）和铁、钙之类的矿物质是另一类的基本营养物质，尽管人体对这一类营养物质的需要量并不像对大量营养物质--各类蛋白质、碳水化合物、脂肪--的需要量的那么大。

有两种维他命：水溶维他命和脂溶维他命，像维生素C和B族维生素这类水溶维他命不会在身体内停留很久，所以人体要经常吸收含有这些维他命的食物。另一方面，维他命A、D、E和K这类脂溶维他命却能在人体里停留很长一段时间，因而就没必要经常地去服用含有脂溶性的食品。

既要得到足够的营养又要减轻体重，办法之一就是服用代和食品，去代替那些脂肪含量过高的食品。例如，不服用全脂奶，而服用脱脂奶，这种脱脂奶里含有和全脂奶同样多的蛋白质和矿物质，只不过是全脂奶中的脂肪已经被除掉了。同样，可以用植物油来代替动物油进行烹调。