'Overweight' is defined as a 'body mass index' of more than 27. Of these, 13% of men and 16% of women are defined as obese - that is, with a body mass index of 30 or more. A proportion of these would be described as morbidly obese, which means that they have a body mass index of more than 35. Click for information on how to calculate your body mass index

Obesity causes health problems and can even lead to early death. Doctors and the government are so concerned that targets have been set in the UK to reduce the number of people who are obese, but these targets are unlikely to be met.

The medical conditions which can develop as a result of obesity vary widely. Some are embarrassing, such as incontinence; others affect your life style, such as arthritis; and others are potentially life-threatening, such as heart disease.

Overall, you are likely to die younger if you are overweight.

Many weight-related medical problems will go away if a person is able to lose their extra weight, and keep it off.

The most important problems which can develop are:

• Diabetes, high blood pressure, heart attacks, angina, high cholesterol levels. These all increase the chances of having a stroke and of dying prematurely, and diabetes also increases the risks of kidney failure and blindness.

• Arthritis, particularly of the back, hips, knees, and ankles.

• Asthma or breathing disorders, which make you breathless and limit what you can do physically.

• A condition called 'obstructive sleep apnoea' where a person unknowingly stops breathing for periods while asleep. This leads to very restless sleep, loud snoring, daytime headaches and a risk of falling asleep during the day.

• In women, obesity can cause painful heavy periods, infertility and urinary incontinence.

• Obesity statistically increases the risks of developing the following cancers: breast, uterus, cervix and ovary in woman, prostate in men, and the large intestine and the rectum in both sexes.

People who suffer from obesity are poorly misunderstood by those of the population who are not obese. There is a common attitude that overweight people are stupid and unable to control themselves. People who are obese are often the brunt of cruel jokes and thoughtless humour, even to the point of suffering abusive comments in public places.

We now know that the medical condition of morbid obesity is a complex disorder, and not simply due to over-eating. The vast majority of people living in the Western World eat more calories than they need but it is only a small proportion who relentlessly lay down every excess calorie in their fat stores. Most people have a mechanism by which their body knows when their stores have been refilled, but there is an unfortunate group of people where this mechanism is defective, and when they eat it can be likened to filling up the bath with the overflow blocked off.

There are of course no fat people in starvation areas of the world, but this is because these are regions with chronic malnutrition and nobody there has access to even adequate calories.

People who are morbidly obese often find it difficult to believe that their problem is a medical disease and not simply due to overeating.