What is obesity? Obesity is most commonly defined in terms of body mass index (BMI).

The BMI is calculated as follows: weight in kilograms divided by height in metres squared.

A desirable BMI is considered to be in the region of 20 to 25. Above this is defined as overweight. And a BMI over 30 is defined as obese.

Having a waist circumference of more than 37 inches if you are a man and 32 inches if you are a woman means you could be increasing your risk of developing heart disease or diabetes.

By losing weight you can cut your risk of heart disease considerably. To lose weight you need to use up more energy than your body takes in from food and drink.

Do this by eating and drinking fewer calories and using more calories by getting more active. Many people attempt short term crash diets to lose weight quickly but these diets involve sticking to an unrealistically restricted menu for a limited period of time.

Any weight loss will be mostly water rather than body fat and will be regained when normal eating is restarted.

Gradual weight loss is the safest and most effective way.

Obesity in England has trebled in the last 20 years according to the British Heart Foundation.

l One in every five adults is obese, which accounts for around eight million people.

l Nearly two thirds of men and more than half of women in England are now either overweight or obese. Health problems linked to obesity are heart disease, some forms of diabetes, high blood pressure, osteoarthritis and a number of cancers.

l Deaths linked to obesity shorten life by nine years on average.

l In 1998, 30,000 deaths were attributable to obesity. Obesity was the cause of 18 million days of sickness absence in the same year and 40,000 lost years of working life.

l By 2010, obesity and its consequences are expected to cost the economy more than £3.6 billion a year.

For more information go to: www.nationalobesityforum.org.uk