Food Data Chart

Fat is also known as lipid and is mainly present in food in a form called 'triglycerides'. Butter and margarine, for example, are almost entirely made up of triglycerides. Triglycerides consist of glycerol and three ('tri') fatty acids. The fatty acids can be mainly 'saturated' as in butter or mainly 'polyunsaturated' as in some margarines (see Figure 47). There are also monounsaturated fatty acids, which occur in quantity in the triglyceride of olive oil and peanut oil.

Food may contain other fats, such as cholesterol and phospholipids, in addition to triglycerides. Lecithin is a phospholipid, made up of glycerol, choline and fatty acids, which again may be mainly saturated or polyunsaturated (see Chart 48 on lecithin).

Fat is energy dense, having an Atwater factor of 9 kilocalories, or 37 kilojoules, per gram. Also, it does not mix with water, so that the food in which it is found tends to be more energy dense because of the relative lack of water. If it is a fat of plant origin, it may be associated with dietary fibre, giving bulk and reducing energy density, as, for example, with the cereal oats that are relatively high in fat for a cereal, but also relatively high in dietary fibre. If the fat is from animal sources, the energy density will be rather high, not only because of the fat and the low amount of water, but also because there is no dietary fibre. It is important to realise that the fat content of meat, and the polyunsaturated to saturated ratio of the fat, varies considerably depending on the source of the meat, the particular cut and trim, and the method of preparation.

If we are very physically active and in need of energy then fat can be a useful source of the energy. Conversely, if we are physically inactive, too much fat in our diet can lead to overweight.

It is possible to eat very little fat and maintain good health. There are traditional dietary patterns in which the contribution of fat to energy intake is as low as 10 per cent. However, in the 'affluent' diet, it may contribute up to 50 per cent of energy intake (see Figure 5). Nevertheless, it must be remembered that the quality of the fat eaten as well as its quantity is important (see Saturated and Polyunsaturated Fats (Chart 9)).

Fat also confers texture and flavour on food, enhancing its palatability. Many flavours are fat soluble; unfortunately it is these desirable properties that encourage over-eating.

FAT INTAKE

The acceptable range for fat intake:

About 10-30 per cent of energy intake, which for a 35-55 year old man would be 30-80 grams of fat per day, and for a 35-55 year old woman would be 20-60 grams of fat per day.