Health Effects of Obesity:

People who are obese or overweight have a higher risk of disease including coronary heart disease, diabetes, hypercholesterolemia, hypertension, gall stones, degenerative joint disease and obstructive sleep apnoea. Life expectancy is reduced by obesity, mainly through the effect of increased weight on related conditions. A recent review showed that even modest weight losses of up to 5 kg may produce important health benefits.4 Weight loss can also reduce the costs associated with treating some of these conditions.

Measurement of obesity:

The body mass index (BMI) is frequently used as a measure of overweight and obesity (see Box). Interpretation of the BMI is limited because factors such as size of body frame, proportion of lean mass, gender, and age are not taken into account. Assessments such as the girth-height ratio (GHR) (waist circumference divided by height) give a measure of central obesity which is associated with an increased risk of cardiovascular mortality, hypertension, and non-insulin dependent diabetes. GHR has been shown, in prospective studies, to be a better predictor of cardiovascular risk than BMI.

Prevalence:

Epidemiological surveys of England indicate that the prevalence of obesity is increasing. In 1994 it was estimated that 13% of men and 16% of women aged 16 to 64 years were obese, around twice the corresponding rates for 1980. The prevalence of overweight in 1994 was 43% for men and 29% for women in the same age group, and is increasing. The prevalence of overweight and obesity in Scotland is similar and data for Wales also reveal an upward trend.

The Health of the Nation strategy for England includes a target to reduce the prevalence of obesity in those aged 16 to 64 years to no more than 6% and 8% for men and women respectively by the year 2005. However, at the present rate of increase, this target is unlikely to be met. Several reasons have been put forward to explain the national trends in obesity. The combination of increased dietary fat and decreased levels of physical activity mean that people do not always expend their energy intake.

This has occurred despite a reduction in the total average energy consumption, suggesting that sedentary lifestyles are the most important factor. Increased eating outside the home, the tendency to eat ‘little and often’, and eating at times when energy expenditure is likely to be low (e.g. late in the evening) may also contribute to this trend High risk groups: Certain groups of people are particularly likely to become obese. Children in families where one or more parents are overweight or obese are at greater risk of developing the condition. Risk of obesity is also associated with social class and level of education. The age-standardized prevalence of obesity in women is 21% in social class V, compared to 12% in class I. A similar trend exists for men (13% in social class V and 10% in social class I).

The likelihood of obesity may vary between different ethnic groups; South Asians are at greater risk of developing central obesity when compared to Afro-Caribbeans and Caucasians. Obesity is also more prevalent in people with learning disabilities such as Down’s syndrome.

Peoples’ risk of becoming obese varies over the life cycle. Smoking cessation is another important risk factor for weight gain. Health professionals may have a negative attitude to people who are obese or feel frustrated because successful treatment is often long-term or elusive and so they may not take positive action to help patients lose weight. Primary health care teams are not always adequately trained in the prevention and treatment of obesity, and may lack relevant resources.

Their importance as a risk factor for major disease and their high and increasing prevalence mean that obesity and overweight generate significant health service costs, variably estimated at around 1–5% of total health care expenditure.

This issue of Effective Health Care summarizes research evidence on the effectiveness of interventions designed to prevent and treat obesity, and to maintain weight loss. Details of the review methods and results are available elsewhere.