Obesity

Obesity is a condition whereby the body’s stores of fat exceed a particular threshold, and is associated with a significantly increased risk of ill health and significantly reduced life expectancy.

The body is required to work much harder in individuals with excess body fat compared with slimmer individuals and this puts it under abnormal levels of strain. As a result obesity can increase the risk of developing mobility and breathing problems and diseases such as cardiovascular disease, type 2 diabetes, some cancers and osteoarthritis (a form of joint disease) amongst others.

Body Mass Index (BMI)

Obesity is defined by the World Health Organisation using a measuring system known as Body Mass Index (BMI) which is defined as weight divided by height squared (kg/m²).

BMI is essentially a measure of relative weight-for-height and although it provides a useful way of measuring obesity it does not always classify people accurately. This is because the BMI system does not measure body fat specifically, and it fails to take muscle tone into account.

As a result, a fit, healthy and muscular individual may inaccurately fall into the obese category as their weight can be relatively high compared with height (due to extra muscle and little fat). 

However for the most part, the BMI system provides a simple and helpful way to indicate whether a person is a healthy weight for their height.

The UK classification for BMI is as follows:

Waist circumference

Although excess fat in general is a risk to health, central obesity (or excess fat around the central part of the body) is associated with greater risks to health, particularly risk of cardiovascular disease.

For this reason measurement of waist circumference is often used as an alternative classification system to BMI.

This provides a guide to the extent of the fat stores around the waist area and gives a more sensitive measure of long-term health risks.

The current recommended cut-off points for Caucasian adults using this classification system are outlined below:

Causation

Obesity primarily results from consumption of more food energy (calories) than the body requires. The additional energy is therefore stored as fat and results in increased body weight and percentage body fat.

The causes of obesity are a subject of great interest since it fast becoming a major public health issue.

Many factors contribute to the development of obesity including:

• Excessive consumption of food
• Consumption of the wrong foods
• Low levels of physical activity
• Poor education of diet and health
• Certain medications
• Stress
• Medical conditions e.g. hypothyroidism

There is also evidence to suggest that genetics may play a role in the development of obesity as specific forms of single genes have been identified which may make some individuals feel more hungry than others or take longer to feel full.

However it is more likely that obesity is caused by the complex interaction of multiple genes and lifestyle choices together.