"Don’t fret Matilda, just take Metabolite and you’ll look cute as ever in your bikini this summer," says Wilber on Metabolite’s Internet ad. Another Web site encourages viewers to take up to eight caplets of a similar-sounding product, Metabolife, to curb appetite and increase energy levels.

Claims made by both are, at best, false. At worst, they could be harmful. Metabolite bases its formula on hydroxycitric acid, a compour little studied in people. One of Metabolife’s main ingredients is ma huang (or ephedra), an herb associated with overstimulation of the central nervous system end even death.

Metabolite, produced by a company called AIM, is widely marketed through pyramid-type schemes. It has three main ingredients: hydroxyci acid (HCA), an herb from India known as Gymnema sylvester and the widely touted mineral chromium.

HCA is a closely relative of citric acid, the component that gives oranges, lemons, limes, and other citrus fruits their characteristic tart flavor. Citric acid is widely distributed throughout the plant kingdom. HCA, however, is found in only a few plant species. One of its main sources is the herb arcinia cambogia. HCA has shown some effect on appetite suppression in preliminary animal studies.

Human studies have not duplicated these results. In one of the few well-designed studies on the use of HCA in people, the herb had no effect on weight loss. In the double-blind study published in the Journal of the American Medical Association, half of the 135 study subjects received 1,500 mg of HCA per day, the other half a placebo. Both groups followed a high-fiber, reduced-calorie diet.

While both groups lost weight during the three-month study, there was no difference in the amount of weight or body fat lost. The research concludes that Garcinia cambogia failed to produce weight loss beyond that observed with a placebo.

The other ingredients in Metabolite have been examined mostly for their role in blood sugar control, not weight loss. The leaves of Gymnema sylvester, a woody climbing plant native in India, have been used for centuries in the treatment of diabetes in that art of the world.

In one small but well-controlled experimental study, glycated hemog a marker for diabetes control, did come down in a small group of diabetic patients taking the herb, compared to those taking a placebo. More research is needed to evaluate the safety and effectiveness of this herb.

The third constituent of Metabolite is the mineral chromium. Widely touted as a weight-loss aid, chromium has shown only a possible but slight benefit in diabetic people who are clinically chromium deficient to begin with.

Metabolife, an entirely different product, contains many herbs, vitamins, minerals and other questionable ingredients, including royal jelly, algae and bee pollen. The main concern with Metabolife centers on the herb ma huang.

For centuries, Chinese herbalists have used ma huang, also known as ephedra, for the early stages of respiratory infections and for certain types of asthma. Traditionally, it was never intended for extended use. Around the turn of the century, the active compound, ephedrine, was isolated from ma huang, making way for modern asthma treatments.

Ephedrine mimics the effects of adrenaline. Symptoms include rapid heart rate, high blood pressure, agitation and insomnia. According to the FDA, exceeding high doses have caused 38 deaths.

The bottom line? As it has always been and likely will continue to be: The best weight-loss strategy is to combine exercise with a diet somewhat reduced in calories, particulary calories from fat and refined carbohydrates. Aim for no more than 1 to 2 pounds of weight loss per week.

At about $50 a month for there supplements, the tried-and-true approach is certainly more affordable, even if it is more work.