Trial Evidence

A. Why Treat Overweight and Obesity?

The recommendation to treat overweight and obesity is based not only on the previously presented evidence that shows overweight is associated with increased morbidity and mortality, but also on randomized controlled trial (RCT) evidence that weight loss reduces risk factors for disease. Thus, weight loss may help control diseases worsened by overweight and obesity and may also decrease the likelihood of developing these diseases. The evidence meeting the panel's inclusion criteria is presented in the following section in the form of evidence statements with a corresponding rationale for each statement. The details of the studies reviewed but not discussed here are provided in Appendix II. 

Many of the RCTs examined by the panel included the use of pharmacotherapy for weight loss. When the panel began its deliberations in 1995, two weight loss drugs, fenfluramine and dexfenfluramine, were being used widely for long-term weight loss, i.e., 14 million prescriptions were given out over 1½ years. However, as of September 1997, the Food and Drug Administration (FDA) requested the voluntary withdrawal of these drugs from the market due to a reported association between valvular heart disease and the use of dexfenfluramine and fenfluramine alone or combined with phentermine (761). In November 1997, the FDA approved the drug sibutramine hydrochloride monohydrate for the management of obesity, including weight loss and maintenance of weight loss when used in conjunction with a reduced-calorie diet. In April 1999, the FDA approved the drug orlistat for weight loss.  Thus, at the present time two weight loss drugs are available for long-term weight loss.  However, due to rapidly evolving information regarding the use of pharmacotherapy for weight loss, the panel decided to present (below) their critique of those pharmacotherapy trials meeting their criteria for consideration.