More than one-third of Americans have a body weight of 20 per cent or more than their desirable weight. Approximately 50 per cent of women and 25 per cent of men are 'dieting' at any one time, generally with little prolonged benefit. Using standard treatments in university settings, only 20 per cent of obese patients lose around 9 kg (about 20 pounds) at 2-year follow-up and only 5 per cent of patients lose about 18 kg (40 pounds). (53) The majority of people who lose weight on a diet gain it all back. There is considerable mortality associated with obesity. This is predominantly due to coronary artery disease and associated risk factors, such as diabetes, hypertension, and hypercholesterolaemia. Numerous lines of evidence suggest strong genetic influences on the aetiology of obesity, (53) accounting for about two-thirds of the variations in weights among studied populations. However, environmental factors are also important. These include low physical activity levels and poor food choices.
Because the odds are against those trying to lose weight, patient selection for weight loss programmes is important. Patients must have a high degree of motivation, which can be assessed by judging how well patients complete pre-programme assignments, such as food diaries and exercise records. When psychiatric disorders are present, these must be treated prior to starting the weight-loss programmes. There is no ideal treatment for weight loss. Weight-loss programmes vary considerably in terms of risk, cost, and efficacy. (53> For most patients with mild to moderate obesity, a multidimensional approach is best, combining diet, exercise, behaviour modification, and social support. Motivated patients with morbid obesity (more than 100 per cent over desired body weight) may be considered for very low calorie diets, with the emphasis on long-term diet, behavioural change, exercise, and social support. (See also Ch§pter...4.10.3. )
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