Extracts from "Clinical Evidence": Obesity
Authors: D. Arterburn
Journal: BMJ (2001)

BackgroundDefinition Obesity is a chronic condition characterised by an excess of body fat.It is most often defined by the body mass index, a mathematical formula that is highly correlated with body fat.Body mass index is weight in kilograms divided by height in metres squared (kg/m 2 ).In the United States and the United Kingdom, people with a body mass index between 25 and 30 are categorised as overweight, and those with an index above 30 are categorised as obese. 1 Incidence/prevalence The prevalence of obesity has increased steadily in many countries since 1900.In England, in 1994, it was estimated that 13% of men and 16% of women were obese. 1 2 In the past decade alone, the prevalence of obesity in the United States has increased from 12.0% in 1991 to 17.9% in 1998. 3Aetiology The aetiology of obesity includes both genetic and environmental factors.Obesity may also be induced by drugs (high dose glucocorticoids, for example) or be secondary to a variety of neuroendocrine disorders such as Cushing's syndrome and polycystic ovary syndrome. 4Prognosis Obesity is a risk factor for several chronic diseases, including hypertension, dyslipidaemia, diabetes, cardiovascular disease, sleep apnoea, osteoarthritis, and some cancers. 1 The relation between increasing body weight and mortality is curvilinear, with mortality increasing in people with low body weight.Whether this is caused by increased mortality risk at low body weights or by unintentional weight loss is not clear. 5 Results from five prospective cohort studies and national statistics for 1991 show that in US adults about 280 000 deaths a year are attributable to obesity. 6Aims To achieve realistic gradual weight loss and prevent the morbidity and mortality associated with obesity, without undue adverse effects.Outcomes We found no studies that used the primary outcomes of functional morbidity or mortality.Proxy measures include mean weight loss (kg), number of people losing 5% or more of baseline body weight, and maintenance of weight loss. MethodsClinical Evidence search and appraisal January 2001. Question What are the effects of drug treatments in adults?Option Centrally acting drugs Summary We found limited evidence from six RCTs that sibutramine is more effective than placebo at promoting modest weight loss in adults with a body mass index between 25 and 40.The weight loss stabilised after six months of treatment and was not sustained after stopping treatment.One RCT found that sibutramine caused modest weight loss in obese adults with controlled hypertension, but we found insufficient evidence about short term safety and no evidence of long term safety.Limited evidence suggests that phentermine and mazindol, compared with placebo, result in modest weight loss over short periods in people more than 15% overweight.Weight regain was found after stopping treatment and after longer treatment periods.We found no strong evidence of serious adverse events associated with either phentermine or mazindol.We found insufficient evidence about either diethylproprion or fluoxetine for weight loss.Dexfenfluramine, fenfluramine, and the combination of If you are interested in being a contributor or peer reviewer for Clinical Evidence please visit the Clinical Evidence website (www.clinicalevidence.org