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Obesity is excess body fat for a given height and gender. It happens when more calories are taken into the body than are burnt up in a given period of time. Once adulthood is reached, everyone has a fairly steady rate of calorie burn-up, called the metabolic rate. This is higher in people who are regularly physically active. This means that someone who works in a very physical job, such as a building-site labourer, may need as many as 40005000 calories per day to keep an even weight. This contrasts with an office worker who uses a car and doesnt exercise, who may need only 1500 calories per day.

If calories in food energy are greater than the calories used every day, the excess energy is stored by the body as fat. This is important as a protection for the body against times of starvation. In developed countries, starvation is rare except in extreme circumstances, so this insurance against hard times is hardly ever needed. Food is plentiful, and a lot of available food is much higher in calories than the human body was originally designed to cope with. The result is that eating more than the body needs is easy. Obesity has become one of the most serious medical problems of the western world.

Obesity can be measured in different ways:

An easy way is just to get on the scales and compare your actual weight with your ideal weight. Any calorie-counting book will give this information.
A more scientific way is to calculate your Body Mass Index (BMI). This is your weight in kilograms divided by the square of your height in metres. In England, people with a body mass index between 25 and 30 are categorised as overweight, and those with an index above 30 are categorised as obese.
Modern gyms and some weighing scales can electronically measure the percentage of your body weight that is fat, and can compare this with what would be ideal for you.
Work out your body mass index number here Careful research based on measurements over a period of 14 years in more than a million people has shown that the risk of death from all causes increases steadily as obesity increases in both women and men of all ages. Men with the highest BMI have three times the risk of dying in a particular year compared with men having a normal BMI.

A report from the World Health Organisation published in April 2001 indicates that obesity and lack of exercise contribute to up to one-third of all cancers of the colon, breast, kidney and stomach. Obesity-related deaths are now second only to those related to smoking. Half of European adults are overweight.

Obesity is not just an adult problem. Recent studies have shown that over the period 198998 there was a rapid spread of obesity in England, the United States and elsewhere in the developed world.

Among 3-to-4-year-old English children there was a 60 per cent increase in the prevalence of obesity. Early childhood obesity is a strong predictor of adult obesity and of serious health risks later in life.

Mild obesity is relatively harmless, but severe obesity can be dangerous to your health in the long term. It can cause both immediate day-to-day symptoms and longer-term health risks.

Symptoms of obesity include:

shortness of breath,
inability to sustain sudden exertion,
excess tiredness every day, and
leg-joint and back pains.
Long-term health risks include increased risk of:

high blood pressure, heart disease and strokes,
high blood cholesterol,
breast cancer in women,
gallbladder disease,
reflux oesophagitis and its complications (the flowing of acid back up the gullet),
arthritis of the back, hips, knees and ankles,
diabetes and poorer control of established diabetes,
polycystic ovary disease, and
reduced life expectancy overall.
The main cause of obesity is excess calorie intake.

Obesity does run in families and the tendency to put on weight is definitely greater in some people than in others who eat a similar diet. However, this is usually due to different metabolic rates.

A gene has recently been discovered that may play a role in obesity, but it is likely that family habits of eating and exercise are key factors.

The Body Mass Index (BMI) is currently the best and most convenient measure of its severity and therefore of the risk to health.

You can work out your own BMI using this calculation:

Measure your height in metres and multiply the number by itself.
Measure your weight in kilograms.
Divide your weight by the answer you got in step 1. The number you are left with is your BMI.
An ideal BMI for most people is between 20 and 25.

Calorie control is the least difficult treatment. There are two aspects to this:

Use a food diary to record everything you eat and drink on a daily basis. Work out your average calorie intake and then cut out 500 calories per day from what youre eating. This doesnt amount to a big sacrifice, and youll still be able to enjoy a range of food. The important thing is to be honest about what youre eating.
Increase the amount of aerobic exercise you do. A rough guide is to do anything that makes you work hard for 30 minutes three times a week. You know youre working hard if youre panting and mildly sweating and have a raised heart rate. Check with your GP that any planned activity is safe for you. Find a way to exercise that you find enjoyable, as this will help you to stick with it.
Find out how many calories you can burn doing the activities you enjoy No weight-loss programme should aim for a loss of more than 1 kilogram per week. Half a kilogram per week is quite respectable, and any weight-loss programme that claims a more rapid loss than this may be unhealthy.

Serious weight loss is a long-term commitment to yourself and it involves time and stamina. It may not be easy, but the results are very rewarding.

Drug therapy

Medical treatment for obesity is available, but only in extreme cases. treatment currently available can only be prescribed if you can demonstrate weight loss on a calorie-controlled diet first.

A lot of stimulant appetite-suppressant drugs have been used in the past, but many have been found to be dangerous. The stimulant drugs are based on amphetamine and carry a risk of sudden death from fatal heart rhythms.

Drugs are sometimes prescribed for patients who are unable to lose weight by changing their diet and increasing their activity levels. Orlistat is a pancreatic lipase inhibitor, which means that it reduces the bodys ability to absorb fat. It may be used in conjunction with a low fat diet to achieve more rapid and greater weight loss. If a low fat diet is not used there may be unwanted side effects. Before your doctor will prescribe Orlistat, you must show that you are motivated to lose weight and have lost 2.5kg prior to treatment.

Another drug recently approved for the treatment of obesity in the UK is Sibutramine. This works in the brain by altering the chemical messages that control how the person taking it feels and thinks about food. It mainly affects two chemicals called noradrenaline and serotonin and promotes a feeling of being full or having eaten enough. It is only prescribed to obese people with a BMI of over 30 or those with a BMI of over 27 with life-threatening conditions such as high cholesterol or Type II diabetes and who have made serious attempts to lose weight by dieting, exercise and/or other changes in their behaviour.

If either of these drugs is prescribed for you, you will also be offered advice, support and counselling on diet, exercise and behaviour changes.


Severe obesity is a chronic condition that is very difficult to treat. Surgery to promote weight loss by restricting food intake or interrupting digestive processes is an option for severely obese people. A body mass index above 40 indicates that a person is severely obese and therefore a candidate for surgery. Surgery also may be an option for people with a BMI between 35 and 40 who suffer from life-threatening cardiopulmonary problems for example, severe sleep apnoea, obesity-related heart disease or diabetes. However, as in other treatments for obesity, successful results depend mainly on motivation and behaviour.

Obese children tend to be obese later in life. Help your children by setting healthy eating habits at home and encouraging regular exercise.
Exercise does not just burn up calories. Regular aerobic exercise resets the metabolic rate at a higher level, so that even in ordinary everyday life the body is using more calories overall. This effect is lost quickly once regular exercise is stopped. Regular exercise will increase your appetite but your increased metabolic rate will more than compensate for it.
Work out your daily calorie requirement from a calorie-counting book, and keep a food diary for a week. Dont change anything about your usual diet, just note the quantity and type of everything eaten or drunk. Work out exactly how many calories youve consumed, and compare this with your expected calorie requirement. This should give you a good guide as to whether you need to cut your calories.

© Queen's Printer and Controller of HMSO, 2005

Crown copyright material is reproduced with the permission of the controller of HMSO and the Queens Printer for Scotland.



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