BACKGROUND: OBESITY AS A PUBLIC HEALTH PROBLEM

Obesity is defined as a body mass index (BMI) of 30 kg/m² or more, where a person’s BMI is defined as their weight in kg divided by the square of their height in metres. Overweight is defined as a BMI between 25 and 29.9 kg/m². In 1980, 6% of men and 8% of women in the UK were obese. In 2000, the respective figures had increased to 21% and 21.4%. Approximately 55% of the adult population is overweight or obese.¹

Obesity causes or exacerbates a large number of health problems, both independently and in association with other diseases.² In particular, it is associated with the development of type 2 diabetes mellitus, coronary heart disease, an increased incidence of certain forms of cancer, obstructive sleep apnoea, and osteoarthritis of large and small joints. The Build and Blood Pressure Study has shown that the adverse effects of excess weight tend to be delayed, sometimes for 10 years or longer.³ Life insurance data and epidemiological studies confirm that increasing degrees of overweight and obesity are important predictors of decreased longevity. In the Framingham Heart Study, the risk of death within 26 years increased by 1% for each extra pound (0.45 kg) increase in weight between the ages of 30 years and 42 years, and by 2% between the ages of 50 years and 62 years.⁴ Despite this evidence, many clinicians continue to consider obesity to be a self-inflicted condition of little medical significance.

Increasing body fatness is accompanied by profound changes in physiological function. These changes are, to a certain extent, dependent on the regional distribution of adipose tissue. Generalised obesity results in alterations in total blood volume and cardiac function while the distribution of fat around the thoracic cage and abdomen restricts respiratory excursion and …