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.

幾乎每一個人在他或她的一生中都有個時候考慮要節食。所有的人，不分性別和年齡，都有個共同之處--要減輕體重，而且要快速減肥。

盡管他們共同的愿望令人覺得好像基本上是好的，但是他們也許并沒意識到，用這些誤導的節食方法，對他們的身體健康來說害大于利。過于嚴苛地節食會破壞人身體內生物化學結構的平衡。之所以會產生這種結果，是因為當人身體突然得到的食物比平時少了許多的時候，身體就會覺得好像受到了襲擊，于是身體就用節約能源支出的辦法盡量設法來保護自己。我們的身體通過減慢新陳代謝速度的辦法來保護自己，亦即減慢把我們所吃的食物轉化成能量的過程。由于以越來越慢的速度給身體供應能源，這些節食的人的身體就逐漸變得非常虛弱，以致弱到什么事都不能做的程度。于是這些節食者很快就會對他們周圍所發生的一切事情都失去了興趣，結果他們的身體對疾病的抵抗能力就變得非常低，以致于他們很容易地就會受到一種又一種疾病的連續襲擊。

絕大多數節食者都知道，像大米、面包、土豆、蛋糕、糖果、各種水果和一些蔬菜等各類食品都含有碳水化合物（即淀粉），因而，都會使人發胖。可是，他們都沒意識到碳水化合物是我們身體的主要的能源，他們都沒意識到這些食品里都含有使我們的身體健康所需要的一些物質的基本成分。結果，他們盡量避免吃類食品，因而他們的身體就變得越來越虛弱、越來越不健康。他們開始有了不能適當睡眠的難題、開始產生了思想情緒上的一些根本變化。在一些較嚴重的病例中，病者甚至開始顯露出有精神病的一些征兆。

說來也真奇怪，那些最嚴格的節食的食譜推薦用人造的甜味劑來代替蔗糖和其他天然的甜食品。事實上，這類人造的甜味劑實質上增大了一個人的食欲，結果反而使人比平時吃得更多。

當然，種種錯誤的節食方法導致了很多問題，但這些事實并不意味著沒有任何一種節食的方法是安全的，也不意味著一切節食方法都對健康有害。恰如其分地節食不但能幫助一個人去掉難看的多余脂肪，而且能幫助一個人把節食的成果保持下去，能幫助一個人過上一種更加充滿了青春活力的、更為愉快的、更為健康的生活。

你很可能會問，到底什么樣的節食食譜才是恰如其分的。噢，簡單地講，有益于健康的節食食譜，就是各種食物都能很好地均衡的食譜。換句話說，就是這種節食食譜中包括了足夠的各種食品，但都不要吃得過多。這足夠的食物足可以提供給我們的身體在適當地發揮其功能時所需要的各類營養物質。這些營養物質中最重要的就是人體所需的 大量的營養物質：各類蛋白質、碳水化合物、各類脂肪。人的身體需要有相當量的蛋白質和碳水化合物作為各器官的建筑材料和人活動的能源。肉、魚、蛋、奶、奶油和各種堅果里面都含有蛋白質，像大米、面包、土豆之類的食品里都含有碳水化合物。人體為了御寒需要脂肪，脂肪能為各種器官提供保護層，但僅有少量的脂肪也就足夠了。

各種維他命（維生素）和鐵、鈣之類的礦物質是另一類的基本營養物質，盡管人體對這一類營養物質的需要量并不像對大量營養物質--各類蛋白質、碳水化合物、脂肪--的需要量的那么大。

有兩種維他命：水溶維他命和脂溶維他命，像維生素C和B族維生素這類水溶維他命不會在身體內停留很久，所以人體要經常吸收含有這些維他命的食物。另一方面，維他命A、D、E和K這類脂溶維他命卻能在人體里停留很長一段時間，因而就沒必要經常地去服用含有脂溶性的食品。

既要得到足夠的營養又要減輕體重，辦法之一就是服用代和食品，去代替那些脂肪含量過高的食品。例如，不服用全脂奶，而服用脫脂奶，這種脫脂奶里含有和全脂奶同樣多的蛋白質和礦物質，只不過是全脂奶中的脂肪已經被除掉了。同樣，可以用植物油來代替動物油進行烹調。