Following World War II, pharmaceutical companies began to evaluate potential agents for weight loss, measuring the amount of weight loss either in absolute terms or relative to initial weight, but always in comparison to the weight loss of a placebo. Weight loss in placebo-treated groups is highly variable from one study to another since the placebo effect is augmented by variations in diet, physical activity and behavioral therapy.
A number of criteria have been proposed for evaluating the response to treatment for obesity. Table 1 lists several criteria for evaluating success in treating obesity, and readers are referred to other publications for a discussion of these approaches. Both the U.S. Food and Drug Administration (FDA) and the Committee for Proprietary Medicinal Products (CPMP) of the European Agency for the Evaluation of Medicinal Products (EMEA) have proposed criteria to be met by drugs approved for the treatment of obesity (7,8). These are summarized in Table 2. The FDA has suggested as evidence for efficacy that weight loss be more than 5% and significantly more than placebo at 12 months. The CPMP has suggested a 10% loss from baseline weight, which is significantly greater than placebo. A number of secondary criteria are also listed along with inclusion criteria and dose-ranging studies. For efficacy trials, both obese men and women should be included who are otherwise healthy with a BMI >30 kg/m2 or >27 kg/m2 if comorbidities such as hypertension or diabetes are present. Both agencies propose a run-in at the beginning of the trial. The CPMP encourages active placebo treatment and does not specify a difference from placebo, as long as the drug effect is significantly greater and > 10% below baseline. | Studies showing maintenance of weight loss are encour- s, aged by both agencies.
Categorical analysis of the percentage of patients who have achieved more than a 5% or 10% weight loss g is similar to the responder analysis used in the initial drug evaluation by Scoville (4) and has also been proposed in the FDA guidance (7) and the CPMP
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