Diet pills, both prescription and over-the-counter, have been used for decades in attempts to modify appetite or metabolism or both, to make weight loss easier. Many of the herbal options have been tested in scientific studies.
Dr. Shirin Hasani-Ranjbar and colleagues at the University of Tehran, Iran, published a systematic review of the medical literature on herbal treatments for obesity. He identified 19 human studies and 58 animal studies for inclusion. The good news is, researchers found statistically significant weight loss from trials of several products, including ginseng, ginger, bitter melon, and ephedra. All 77 studies showed loss of body weight or body fat or both, except for one study which “seemed to have problems with the study design”, according to Hasani-Ranjbar.
The bad news is, it doesn't take much to be statistically significant. An average weight loss of 7.7 pounds in a 12-week trial was the best result in the medical literature reviewed. More bad news: this result was achieved with ephedra, a stimulant that has been banned in the United States since 2004 because of its harmful cardiovascular effects.
Dr. Ano Lobb of Dartmouth Medical School, New Hampshire, pointed out that the studies showing positive results for weight loss supplements have several limitations: small numbers of participants, short duration of the trials, and potential conflict of interest since the funding comes from companies that sell the supplements. The funding issue also applies to prescription drugs.
Losing weight is one thing; keeping it off is another. Dr. J. D. Fernstrom at the University of Pittsburgh, Pennsylvania, explained that many stimulant drugs decrease appetite in the short term and appear to be effective weight loss treatments. Over the long term, however, the body develops tolerance to the appetite suppressive effects of stimulants. As the pills stop working, the dieters gain weight.
Hasani-Ranjbar recommended more research on herbal treatments for obesity. However, he noted that “Lifestyle modification is still the safest and [most] efficacious method of inducing a persistent weight loss.”