OBESITY

by Dr Honor Merriman MB BS, MRCGP, MFFP, General Practitioner, Headington, Oxford

The simplest definition of obesity is based on the body mass index (BMI). This is calculated from the patient's weight (kg) divided by the square of the height. The normal range for adults is from 20 to 24.9. Any patient with a BMI greater than 25 is considered to be obese, and this is graded from mild (grade 1) to severe (grade 3). Patients with grade 3 obesity have the greatest health risks, and need the most intensive treatment.

Prevalence

Current Department of Health (DoH) statistics show that about 13% of men and 16% of women aged between 16 and 64 years have a BMI greater than 30 (grade 2 or 3 obesity). As obesity is recognised as a risk factor for cardiovascular disease and stroke, its prevalence has been monitored by most general practitioners in their health promotion activities. Although the reduction of obesity is a "Health Of The Nation" target, there has been no improvement since the target was set, and the DoH has recently announced that obesity is now more prevalent than at the start of the project.

Health risk

Obesity causes social and medical problems. It is less acceptable to be obese in Western society than to have a normal or low weight. Obese individuals may have difficulties at work. Their personal relationships are also affected. Low self-esteem commonly follows, and a vicious cycle may result as some obese patients tend to eat for comfort when they have social difficulties.

Obese patients are at greater risk than normal-weight patients of developing many medical problems, including:

• cardiovascular disease
• early death from myocardial infarction
• hypertension
• diabetes: types 1 and 2
• abnormal oestrogen metabolism
• endometrial carcinoma
• breast cancer
• menstrual irregularity
• menorrhagia
• mechanical problems (osteoarthritis, varicose veins, hiatus hernia, reduced lung compliance, obstructive sleep apnoea)

They have a greater risk of early death from cardiovascular disease, cancer and, in younger people, from accidents or suicide. The degree of risk of early death is directly proportional to how obese the patient is. (1) When all these health problems are listed, it is clear that there is significant risk to the individual in remaining obese.

Cardiovascular disease

Many of the risk factors for cardiovascular disease (hypertension, hyperlipidaemia, and diabetes mellitus) are made worse by obesity. The adverse effects of raised blood pressure and hyperlipidaemia are additive in obese patients. If the patient also smokes, the risk of developing coronary artery disease is particularly high. Grade 2 and 3 obesity is a risk factor in its own right in people over the age of 60 years. Younger people with all grades of obesity have an extra risk of cardiovascular disease.

Diabetes

There is also a well established link between obesity and diabetes. Familial predisposition is well recognised for both type I and type II diabetes, and people from affected families who become obese increase their risk of developing type II diabetes. (2)

Gallstones

The development of gallstones is also linked to obesity. This is, in part, due to increased excretion of cholesterol in the bile. Hormonal factors (such as pregnancy and the oral contraceptive pill) also increase biliary cholesterol secretion. The combination of being female, over 40 years old, and obese, is well known as a cause of gallstones.

Hormonal problems

Abnormalities of oestrogen metabolism in obese women can cause menstrual irregularities and menorrhagia. They may also cause the increased incidence of endometrial and breast cancer.

Mechanical problems

Mechanical problems (such as osteoarthritis in weight-bearing joints, varicose veins, and hiatus hernias) are common in obese patients. Reduced lung compliance makes it more difficult for these individuals to take exercise. In the most extreme cases, patients develop hypoxia and respiratory failure. Obstructive sleep apnoea due to upper airway obstruction is more common in obese patients and adds to their cardiovascular risk. (3)

Investigating the obese patient

The causes of obesity include:

• excessive calorie intake
• myxoedema
• Cushing's syndrome
• polycystic ovary syndrome
• medication (oral contraceptive pill, corticosteroid analogues, sulphonylureas, tricyclic antidepressants, pizotifen)

Most patients seen by general practitioners are obese simply because they eat more calories than they need. Some disorders (such as myxoedema and Cushing's syndrome) may present as mild obesity, and patients should be investigated if they have symptoms of hypothyroidism (such as feeling cold, loss of energy) or features suggestive of hypercortisolism (such as truncal obesity, striae). Tiredness may not be due to being overweight alone, and a full blood count may be indicated to exclude anaemia.

Women with infrequent or absent menstruation, acne, hirsutism, and obesity, may have the polycystic ovary syndrome, which requires treatment to restore fertility. These women also benefit from weight loss, as this may help to correct the associated hyperinsulinism and dyslipidaemia.

Obesity may also be caused by prescribed medication. The oral contraceptive pill may be associated with a small weight increase, and corticosteroid analogues may lead to a large weight gain. Other drugs that may cause weight gain include sulphonylureas, tricyclic antidepressants, and pizotifen.

Nevertheless, the assessment of the obese patient should normally be directed more towards detecting associated health risks, rather than looking for a cause of the obesity. Blood pressure measurement and urinalysis (to exclude diabetes mellitus) are essential, and plasma lipids should be checked if there is a personal or family history of cardiovascular disease.

Important areas to cover in the assessment of an obese patient include:

• past history of cardiovascular disease
• family history of cardiovascular disease
• medication
• smoking
• alcohol intake

During the examination, check:

• height
• weight
• waist circumference
• blood pressure

Look for clinical features suggesting thyroid or adrenal disease, as well as acne, hirsutism (signs of polycystic ovary syndrome), pallor, and signs of hyperlipidaemia.

Difficulties to overcome before treatment

Many people see obesity as a self-inflicted problem, in which case it would be acceptable to issue the patient with an appropriate diet sheet and leave them to it. Motivating the primary healthcare team to offer extra support to these patients may be difficult. Most overweight patients are cared for by doctors and nurses in the community. In many parts of the country there are no specialist services to help those patients who are severely obese. Community dietitians can only help with the more complicated cases, because there are not enough of them to care for all patients. Is there an underlying fear that, if an improved service is offered to obese patients in primary care, a huge number of patients will be detected who will swamp local resources?

Finally, the emotional outlook of many obese patients colours consultations with them. They often have a resigned, despairing attitude which readily transfers itself to the doctor or nurse, and negates efforts to change their eating habits.

Aims of treatment

The primary aim of treatment is to reduce the risks to the patient's health. Weight reduction improves survival rates in younger people with all grades of obesity. In patients over the age of 60 years, the effect is less pronounced, but the improvement in quality of life is significant, particularly because of improved mobility and relief of pain in osteoarthritic, weight-bearing joints.

To aim for a BMI between 20 and 24 (9) may be unrealistic in some patients. However, risk reduction can be achieved by relatively moderate weight loss. Studies have shown significant improvements in cholesterol, triglyceride, and high density lipoprotein cholesterol levels, if patients reduce their weight by 5 to 10%. (4) In other studies, raised blood pressure has been brought within the normal range by moderate weight loss. (5)

It is important that smokers stop smoking, even if it delays reaching the target weight. Alcohol intake also needs to be reviewed, as a considerable number of calories may be taken in liquid form.

Dietary advice

Reduced calorie intake is the basis of all diets. The word diet may not help, because this implies a short-term change when what is needed is life-long attention to eating habits. It is best to suggest simple adjustments to the patient's current eating pattern. Most energy should come from complex carbohydrates (providing at least 30 g of fibre per day), and less than 35% should come from fat.

There are many diet schedules available, and every hospital dietetic department will be able to supply suitable guides. High-fibre meals three times a day are better than one meal a day. High-calorie snacks between meals should be avoided. Gradual, steady weight loss is the aim. Very low calorie diets cause loss of fat-free body tissue, and have been associated with sudden death in otherwise fit people.

Exercise

Exercise has many benefits, most obviously because energy is expended with regular exercise. It also tends to modify inappropriate appetite and food intake. The conversion of adipose tissue to muscle as a result of exercise causes a reduction in total body fat and in upper body obesity (thought to be a particular risk for cardiovascular disease). Exercise has a beneficial effect on lipids and on blood pressure, and also improves insulin sensitivity. People who exercise regularly feel better, and have improved morale. The form of exercise should be guided by the physical state of the patient. Older patients with osteoarthritis may find swimming better than weight-bearing exercise. Twenty minutes of brisk walking each day is better than nothing.

Psychological support

Obesity is not classified as an eating disorder in the same way as anorexia and bulimia are. Attention to the psychological aspects of overeating is, however, valuable. Overeating may just be a bad habit, but people who eat when they are not hungry may be responding to stresses such as boredom, anxiety, or anger. A simple way to detect the cause of the overeating is to ask the patient to keep a dietary diary. Patients should record everything they eat or drink for a minimum of one week, including main meals and snacks. They should be encouraged to write down what they felt when they ate the snacks. The diary can then be used to suggest improvements to the diet in terms of what is eaten and the pattern of eating. Where there are signs that the patient is eating for comfort, other approaches to relieve these symptoms should be considered. In a few patients, the obesity may be a symptom of a severe emotional disorder which needs treatment before the obesity can be tackled.

Obesity in children

Obesity in children may result from unresolved eating problems in infancy. The optimal age for tackling these problems is between the ages of 5 and 12 years. An educational programme involving the whole family is needed.

The primary health care team

A flexible approach is essential. Some patients will respond to individual attention, and the severity of their obesity will be such that they will need it. Others, who have mild obesity, may find treatment in a group more helpful.

Doctors, practice nurses, health visitors, and midwives, are all involved in weighing patients, and each may be chosen by the patient as the most appropriate help. Individual help should take place on a regular basis (maybe once a fortnight). The patient should be weighed on the same scales each time, and should be given a long enough appointment to talk through the practical aspects of altering food intake. The patient's partner should come to the sessions and be as involved as possible.

Groups based at the practice premises may be run by a practice nurse or dietitian. Patients then have chance to weigh-in every week and support other group members. Patient-run groups are also successful. The group can use their activities to support charities, as well as to chart their successful weight loss. The general practice team can provide additional help and information. Groups based away from the practice premises can also be effective. The best known group of this type is Weight Watchers.

Medication

The use of medication to control appetite should take second place to appropriate dietary advice and behaviour modification. It should only be used for short-term treatment of grade 3 obesity.

Phentermine (Duromine or Ionamin) are controlled drugs, and can cause dependence as well as making patients anxious and restless. Fenfluramine (Ponderax) also has adverse emotional effects on patients. Its derivative, dexfenfluramine (Adifax), has fewer side-effects. Dexfenfluramine potentiates the effects of serotonin in the brain, which reduces hunger and the desire for carbohydrates. Combined with improved eating habits, it can be valuable in the early treatment of severely obese people. It should not be used for more than three months. Other new agents are being developed (such as sibturamine) in an attempt to suppress the appetite without side-effects.

Other approaches

Jaw wiring has been used in specialist centres for the morbidly (grade 3) obese. Waist cords may help to maintain weight loss. The cord is an inextensible nylon cord fitted round the waist which becomes tight if weight is gained.

Conclusion

The management of obesity in primary care is difficult, but the risks to obese patients are so severe that doctors should not be deterred.

A behavioural approach together with dietary advice seems to be suitable for most patients. Medication should be reserved for very obese patients, as most available drugs have many side-effects. Support for the patient is important. This may be on an individual basis or in groups, depending on the needs of the patient and on local resources.

References

1. Royal College of Physicians. Report on Obesity. J R Coll Phys 1983; 17: 1-58.
2. Colditz GA, Willett WC, Stampfer MJ et al. Weight as a risk factor for clinical diabetes in women. Am J Epidemiol 1990; 132: 501-13.
3. He J, Kryger M, Zorick F et al. Mortality and apnea index in obstructive sleep apnea. Experience in 385 patients. Chest 1988; 94: 9-14.
4. Wood PD, Stefanick ML, Dreon D et al. Changes in plasma lipids and lipoproteins in overweight men during weight loss through dieting as compared with exercise. N Engl J Med 1988; 319: 1173-9.
5. Stamler J, Farinaro E, Mojonnier LM et al. Prevention and control of hypertension by nutritional-hygienic means. JAMA 1980; 243: 1819-23.
6. Garrow JS. Obesity and related disease. London: Churchill Livingstone, 1988.