Tiscali: Calorie Counter

For many years, doctors and successful dieters alike have acknowledged that the healthiest and most effective form of weight loss is to combine a Calorie-controlled diet with regular exercise. Now that the body's metabolism is understood more fully, the informed dieter and health-conscious eater wants to know not only the Calorie content of food but also its composition.

The body can be compared to an engine, and the 'fuel' it uses is food. About half the energy provided by food is used to keep the body functioning normally; the other half is taken up by activity such as work and recreation. Generally speaking, active people use more energy and, therefore, need to eat more to meet their energy requirements. If a person consumes more energy than he or she expends, the excess will be stored by the body as fat, and the person will put on weight. Conversely, if a person consumes less energy than he or she expends the extra energy will be taken from the body's fat stores, and the person will lose weight.

The energy provided by food and burnt up by the body is generally measured in Calories, also called kilocalories (kcal). It has been calculated that one pound of body fat is equal to 3500 Calories, so for every pound required to be lost, 3500 Calories must be burnt up or cut out of the diet over several days. The Hourly Activity & Calorie Guide gives the average number of Calories used in an hour whilst taking part in certain activities. However, the rate at which the body uses up Calories varies from person to person, and depends on many factors such as a person's age, sex and general state of fitness, as well as the composition of their diet.

The food that we eat is made up of three major kinds of nutrients: proteins, carbohydrates and fats. It also provides the body with vitamins and minerals; these are called micronutrients because they are required in much smaller quantities. Nutrients all have important functions within the body.

Proteins are the building bricks of the human body. The cells of our bones, muscles, skin, nails, hair and every other tissue are made up of proteins. Many vital fluids, such as blood, enzymes and hormones, also contain proteins. There is an enormous variety of different kinds of protein, each made up of a special combination of components called amino acids.

The protein in our food is broken down into its component amino acids by the digestive system, and new proteins are synthesized by the body. The best sources of protein in the diet are meat, fish, eggs, milk and other dairy products, corn, lentils and other pulses. The protein obtained from animal sources contains more amino acids than protein from plants. Vegans, therefore, have to eat a wide variety of foods in order to ensure that their diet includes the full complement of amino acids.

Nutritionists recommend that protein represents 10% of the body's daily energy intake. This means that if a person consumes about 2400 Calories a day, 240 of those Calories should be provided by the protein in their food. One gram of protein provides about 4 Calories, so that person needs to consume about 60 grams of protein a day. Many people eat more protein than this, and there is little evidence to suggest that eating too much protein is a health risk. However, a diet low in protein is harmful, particularly to the young who are still growing.

Carbohydrates are made up of different kinds of simple sugars, such as glucose. The scientific name for the sugar that we add to our food is sucrose; one molecule or unit of sucrose is made up of two units of glucose. Carbohydrates can be divided into two different categories. The first category, which we will simply call carbohydrates, are known as available carbohydrates because the body can obtain energy from them. The second category, usually called dietary fibres, are known as unavailable carbohydrates because they are indigestible.

Available carbohydrates are important sources of energy for the body. They are broken down by the digestive system into the individual simple sugars; then they can be metabolized immediately to release energy, or they can be converted into fat and put into the body's energy stores. Starch is a form of carbohydrate, and starchy foods such as wheat, rice, pulses and potatoes Honey, sugar, sweets and sweetened soft drinks contain very high levels of carbohydrates, but they provide the body with virtually no other nutrients. For this reason, energy from these sources is sometimes referred to as 'empty calories'.

Although the body can obtain energy from a diet that contains no carbohydrates, they are still an important part of the diet, not least because foods rich in carbohydrates are usually good sources of micronutrients. For example, grains provide B vitamins, and fruit is an important source of vitamin C. Nutritionists recommend that 50% of the body's energy requirements are derived from carbohydrates. If a person consumes 2400 Calories a day, 1200 of those Calories should be provided by carbohydrates in their food. One gram of carbohydrate provides about 4 Calories, so that person should eat about 300 grams of carbohydrates a day.

Unavailable carbohydrates, or dietary fibre, cannot be broken down by the digestive system. Dietary fibre adds bulk to food and contributes to the 'full' feeling after a meal. Although it does not contain any nutrients it is an essential part of the diet and it has a number of beneficial effects, especially assisting the regular and comfortable evacuation of the bowels. Certain kinds of dietary fibre, such as oat bran, are believed to lower levels of cholesterol in the blood. Foods that contain high levels of dietary fibre are, anyway, usually good sources of other nutrients and micronutrients. They include wheat bran and bran cereals, dried fruits, nuts, pulses, and leafy green vegetables.

The average UK diet provides only about 12 grams of dietary fibre a day. Nutritionists recommend that this figure should be nearer 30 grams. If the intake of dietary fibre is increased too rapidly it may cause flatulence and diarrhoea. A very high consumption of fibre may impede the absorption of certain vital minerals.

Fats in food are the perennial enemy of the dieter. Fat has a very high energy value: 1 gram of fat provides 9 Calories; this is more than twice the calorific value of 1 gram of protein or of carbohydrate. The fat obtained from food is only broken down and used as energy when other sources of energy all the fat in the diet is not converted into energy, it is simply laid down in the body's fat stores. A high intake of fats will, therefore, cause weight gain.

Vegetable oils, dripping, lard, butter, margarine, cream and nuts are all high in fat. Some meats also have a high fat content, but this can usually be reduced by trimming away the visible areas of fat before or after cooking. Fats obtained from animal sources, such as butter and cream, have been associated with an increased risk of coronary heart disease and of cancer if they are consumed in large quantities. Oils obtained from plants do not have this property, and certain vegetable and fish oils are thought to actively reduce the risk of heart disease.

Fat represents about 40% of the total energy intake of the average UK diet. This figure is much higher than it needs to be for the body's requirements. The body needs fat as an energy store and for the formation of cell membranes and the protective sheath that surrounds nerves, as well as the synthesis of certain hormones and enzymes. Most fats can be synthesized from excess carbohydrate and protein, but there are special fats called essential fatty acids which must be obtained from the diet. In order to ensure that these substances are included in the diet, fat should represent at least 2% of the body's energy intake.

However, a diet this low in fat would be unpalatable and difficult to prepare; nutritionists recommend that fat provides about 20% of the daily intake. This means that if a person consumes 2400 Calories a day, 480 of those Calories should be provided by fat in their food. Since 1 gram of fat provides 9 Calories, that person should eat about 53 grams of fat a day.

Our weight charts will help to give the dieter a realistic target. Anyone considering trying to lose a lot of weight should consult their doctor, and those just keen not to overdo it should remember that the best way to lose weight is to eat in moderation and to take regular exercise.