2. To reduce body weight 3. To promote long-term maintenance of weight loss
ASSESSMENT OF OBESITY
Measurement of height and weight, in order to determine the BMI, is the initial step in the clinical assessment of obesity. Waist and hip circumference measurements provide information as to the distribution of weight, with a waist circumference measure of >102 cm in men and >88 cm in women associated with increased risk of CHD (39). More sophisticated measures of body fat can be made using other techniques such as bioelectrical impedance, dual energy X-ray absorptiometry, densitometry and isotope dilution, although these techniques tend to be expensive, complex and are generally confined to a research setting.
RISK FACTORS FOR OBESITY The patient’s age is important in determining risk from obesity and generally there is greater risk from obesity in those under 40 years of age.
Taking a weight history can ascertain the onset and duration of obesity as well as the pattern of weight gain and weight loss throughout the individual’s life.
Longitudinal studies have shown that weight gain confers a greater risk of cardiovascular disease than an unchanging level of obesity (40).
In addition, the longer the duration of obesity the more difficult treatment may be.
Gender is another variable that impacts on the development of obesity, with women generally having a higher prevalence of obesity compared to men, especially in middle age (41).
Reproductive function can be affected in younger women, with menstrual disorders including irregular bleeding and amenorrhea being more common among obese females.
Various medical/genetic causes of obesity must also be considered.
Endocrine conditions associated with weight gain include hypothyroidism, Cushing’s syndrome, hypogonadism in the male, polycystic ovary syndrome (PCOS) in the female and growth hormone deficiency (42).
Rare genetic causes of obesity include Prader, Willi syndrome, Bardet, Biedl syndrome and Cohen’s syndrome.
Diabetes can be an obvious consequence of the severe obesity associated with such syndromes.
FAMILY HISTORY It is important also to establish a family weight history. Estimates of the heritability of obesity vary, with some early estimates as high as 70% (43) to
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more recent estimates of 30, 40% (44,45). The children of those with diabetes are at an increased risk of developing the condition and the involvement of the whole family in treating and preventing obesity should be encouraged.
ASSESSMENT OF CO-MORBIDITY It is important to determine the presence of any cardiac risk factors such as hypertension, hyperlipidaemia and cigarette smoking and to provide appro- priate advice and therapy.
The physical symptoms of obesity include reduced mobility, joint pain, chest pain, breathing difficulties and sleeping difficulties, and these should also be assessed.
Conditions such as osteoarthritis and gastrointestinal disorders such as gastric reflux can also be exacerbated by excess weight.
As well as measures of glycaemic control, measurements of biochemical indices such as lipid levels and thyroid levels are advisable.
DIETARY HISTORY A history of eating behaviour and if appropriate a current diet history can provide information as to the eating patterns and food preferences of the individual and can be used to begin to identify the changes needed.
Encouraging patients to monitor their own food intake and activity patterns can be helpful in providing feedback to the patient on how to improve the nutritional quality of the diet and how to identify and overcome barriers that lead to overeating.
Consideration should also be given to socio-economic and cultural factors that influence the eating patterns of an individual, particularly since diabetes is strongly associated with the Asian and African, Caribbean populations in the UK.
Eating disorders and in particular binge eating are common among the obese, with prevalence estimates of 23, 46% in those seeking treatment (46).
Binge eating disorder has also been reported to be associated with Type 2 diabetes, but would appear to precede Type 2 diabetes in most patients.
The prevalence of binge eating disorder in those with Type 2 diabetes was recently estimated as 10% among a sample of 322 German patients (47).
Other forms of disordered eating, including night eating syndrome, should also be considered when assessing an obese individual.
ASSESSING MOTIVATION TO LOSE WEIGHT When conducting an assessment of obesity, it is important to establish the ability and motivation of the individual to make lifestyle changes at that time. The style of the therapist can be crucial in facilitating behaviour change (48) and enhancing the confidence of the individual to be able to sustain changes. Key skills include the core counselling skills of listening and reflecting,
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motivational interviewing techniques, as well as strategies such as cognitive behavioural therapy (CBT).
OBESITY TREATMENT
It is a basic fact that excess body fat results from an imbalance between energy input and energy output.
Any obesity treatment will therefore have to attempt to reverse this imbalance so that energy intake is less than energy expenditure.
However, obesity is a complex condition that involves the integration of social, behavioural, cultural, physiological, psychological, metabolic and genetic factors.
It follows therefore that no single treatment option is likely to address all components.
Treatments need to be interwoven so that dietary counselling, physical activity, behavioural therapy, pharmacotherapy and even surgical treatment are provided in tandem.
A multidisciplinary approach to weight management is generally advocated, although where resources are limited this may not always be achievable.
DIETARY MANAGEMENT The dietary management of diabetes is focused on measures that will improve glycaemic control.
The high-fibre, high-carbohydrate and low-fat advice advocated is a type of dietary regimen which should also encourage weight loss.
Increasingly, attention has also been given to the glycaemic index (GI) within the dietary management of diabetes.
It is interesting to note that diets based on low glycaemic foods have been shown not only to improve blood glucose control but also to cause greater weight loss than diets based on high GI meals (49).
Ultimately, in order to lose weight, a reduction in overall energy intake is required.
A useful first step, therefore, is to calculate the energy requirements of an individual based on their current body weight, age, gender and activity levels using prediction equations such as those recommended by Lean and James (50).
Aiming for a weight loss of 0.5, 1 kg/week involves reducing energy intake by 500, 1000 kcal/day.
In conjunction with the individual, it is possible to devise an eating plan which will provide a modest reduction in energy intake and be more achievable than standard prescribed energy diets.
Blanket energy prescription, usually 1200 kcal for women and 1500 kcal for men, has been shown to produce significant weight loss in several studies (51, 53).
For those most overweight, however, a standard energy prescription can be several thousand calories below their requirements.
Frost et al. (54) compared a 1200 kcal dietary prescription to a daily energy deficit of 500 kcal in a group of patients attending a dietetic weight management clinic.
Their results showed that those in the daily deficit group achieved a greater weight loss than those in
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the standard prescribed diet group, suggesting a greater compliance to a more modest energy reduction.
As well as aiming for a realistic reduction in energy intake, the nutritional quality of the diet is important and it should provide all of the essential nutrients in order to maintain health.
Several studies have looked at the effect of very low calorie diets (VLCDs) in the treatment of diabetes (55,56).
VLCDs are ‘nutrient-enriched’ regimens, usually in the form of liquid drinks, which aim to provide less than 3300 kJ/ 800 kcal of dietary energy per day.
Mean weight losses with a VLCD range from 1.5, 2.5 kg/week, so that use over 12, 16 weeks should produce close to a 20 kg weight loss.
In practice, however, such weight loss is not always observed, indicating that as with other dietary regimes, this change is difficult to sustain.
Maintenance of weight loss may be of particular concern with a VLCD regimen, due to the significant calorie reduction from actual energy requirements and the sharp divergence from normal eating patterns (57).
Following the termination of severe energy restriction, subsequent overeating could be a compensatory response to the physiological or psychological effects of food deprivation (58).
VLCD regimens have been used in many short-term studies with considerably fewer examining their long-term use.
Often improvements in glycaemic control in the obese diabetic patient are seen within days of caloric restriction, suggesting that calorie restriction as well as actual weight loss is responsible for improvements in blood glucose control.
The mechanisms for improved glycaemic control through calorie restriction are unclear, but are thought to relate to a reduction in hepatic glucose output.
Wing et al. (59) studied a group of 93 obese Type 2 diabetic patients who were randomised to receive two different degrees of calorie restriction, i.e. 400 or 1000 kcal/day.
The study showed that the degree of calorie restriction, independent of differences in the magnitude of weight loss, affected fasting glucose levels and insulin sensitivity.
It is recommended that VLCDs are carried out under medical supervision only, with consideration given to long- term maintenance of weight loss.
Whichever type of dietary regimen is adopted it is important to remember that dissemination of information and direct persuasion alone are unlikely to bring about sustained dietary change (60).
Adopting a counselling approach and developing skills in communication that facilitate behaviour change are recommended to help people through the process of change necessary in obesity treatment (61).
BENEFITS OF ACTIVITY Regular physical activity has been shown to confer a protective effect against the development of diabetes, particularly in those individuals who are at greatest risk of developing the condition (62, 65). For the obese individual who has already developed diabetes, regular physical exercise also has several