Fat

Fat and cholesterol are the big bogeymen of the dietary world but eliminating them from your diet entirely is not a good idea unless you wish to have a really miserable existence. As with many things, however, moderation is good.

• A number of essential vitamins are fat-soluble (A, D, E and K). Your body can only absorb them when there is some fat in the diet to act as transportation as food passes through the alimentary tract. The body also uses fatty material in the liver to store reserves of these vitamins. Taking these vitamins as supplements, however, can be dangerous as fat soluble vitamins are not washed out of the body in the urine as water-soluble vitamins are. As a result, levels can build up until toxicity effects occur.
• Cholesterol is part of the steroid chemistry of the body - note the "sterol" part of it's name. Other quite important steroids are testosterone, oestrogen and progesterone - you'll want the biochemistry involving these to work properly.
• Many flavourings are fat-soluble too - the essential oils of many herbs and spices are prime examples. One important part of the cooking process if drawing these oils and fat-soluble flavourings out of the seasonings and dispersing them into the other components of the dish. Neglecting this fact explains why some diet recipies taste a little flat - often a very small amount of oil can improve the flavour markedly. Oils also tend to cling to food rather than seeping away or evaporating as water does, binding the flavours to the solid components of the food. An oil spray is a very good way of dispersing a small amount of oil throughout a dish during preparation.
  
• Fats/oils also have one other important property in terms of cooking - they have a much higher boiling point than water. This allows food to reach much higher temperatures and a variety of chemical changes such as caramelisation or browning can occur, giving food that cooked flavour. Again, many overzealously fat-reduced recipies exhibit a "raw" or "boiled" flavour as a result of neglecting this point. Often this can be worked around by judicous application of "dry" heat - for example, roasting spices before incorporation or flashing food under the grill for a bit. Again a little oil spray can also work wonders.