In addition, some weight loss supplements have  potentially dangerous interactions with prescription or over-the-counter  medications or foods. In fact,  multiple-ingredient products account for 85 percent of the weight loss  supplement market. Limited Federal Efforts Have Focused More on Oversight of Advertising and Labeling than on Oversight of Safety

Federal oversight, research, and education efforts to protect and inform  consumers about the potential risks associated with the use of some  weight loss supplements have been limited. Two publications,  “Tips for the Savvy Supplement User” and “An FDA Guide to Dietary  Supplements,” together provide a general overview of the dietary  supplement industry. State Statutes and Regulations

States have adopted statutes and regulations specific to the sale of certain  weight loss supplements. State, Local, and Private Lawsuits

Some state attorneys general and local district attorneys have sued  marketers or manufacturers of weight loss supplements over marketing  claims. Consequently, little is known about whether  weight loss supplements are effective, but many of them have been  reported to be associated with the potential for physical harm. However,  as the upward trend in sales and use is expected to continue, more  consumers may be at risk of adverse events related to use of the  supplements.
What GAO Found

Since the enactment of the Dietary Enactment Supplement Health and Education Act in 1994, U.S. sales of weight loss supplements have increased steadily. The sales of weight loss supplements--reported to be the fastest growing segment of the dietary supplement industry--increased 10 to 20 percent annually from 1997 to 2001, and industry officials expect that rate of increase to continue. Little is known about the effectiveness of weight loss supplements, but some supplements have been associated with the potential physical harm. Health consequences may result from the use of the supplement itself or from the interaction of the supplement with medications or foods. Federal and state activities related to weight loss supplements have been limited and have focused on oversight of marketing rather than on oversight of safety. In addition, several states have statutes or regulations in effect or pending to restrict the sale of some weight loss supplements. Some state attorneys general and local district attorneys have sued the manufacturers of supplements marketed with weight loss claims, and individuals have sued over injuries.