The makers of natural weight-loss products use a wide range of plant and animal extracts, vitamins and minerals that they promise will speed metabolism, suppress appetite, make you feel full and convert fat into muscle. Some of these ingredients are sold individually, but the bestsellers of the weight-loss category are often diverse and constantly changing combinations touted as "proprietary formulations."
The labels rarely clarify the contents. Where details and dosages are provided at all, they are frequently presented as a bewildering mix of Latin plant names, trademarked monikers for a company's own mix of ingredients and, often, invented words that sound scientific but mean nothing to chemists or pharmacologists. Hydroxycut's "Hardcore," for instance, touts its "norepidrol intensity focus blend" as an aid to focus and attention. Another supplement, TheraStress, declares that its active compound of "adaptogens" helps fight weight gain brought on by stress.
For consumers seeking full disclosure, these labels may as well declare the product is made of genuine atoms.
The following are among those ingredients most frequently used in these formulas, along with what's known about their possible effects -- good and bad.
Seldom acknowledged on the labels of dietary supplements promoted for weight loss, caffeine is almost uniformly their key ingredient. Its sources are many and extremely varied: green tea extract (or Camellia sinensis), guarana, yerba mate and kola nut to name a few.
Consumer Lab's 2005 review of dietary supplements for weight loss measured caffeine levels in two popular weight-loss products still on the market -- Zantrex-3 ("The Ultimate Ephedra Replacement") and Xenadrine EFX. Zantrex-3 was found to have 1,223 milligrams of caffeine in a day's recommended dosage -- equivalent to 30 cans of cola. Xenadrine EFX was found to have less -- 448 milligrams -- but still 1 1/2 times the caffeine associated with adverse effects such as heart palpitations and sleep disruption.
In studies, high doses of caffeine have been shown to decrease appetite, but the effect doesn't last long. The chemical also acts as a diuretic, prompting the release of retained water, which leads to short-term weight loss.
"There is some evidence" that caffeine can contribute to temporary weight loss, says Barbara Corkey, an obesity researcher at Boston University who directs the Boston Obesity Nutrition Research Center.
"What caffeine can do is stimulate lipolysis, the breakdown of lipids, and that should, in theory, have a beneficial effect. But in practice it's useless: The body is very smart about compensating for that. . . . so it's not a long-lasting, permanent effect."
After the FDA banned the sale of ephedra and other products containing ephedrine in 2004, marketers of dietary supplements for weight loss widely proclaimed extracts from the peel of bitter orange (Citrus aurantium) "the next ephedra." They may have been more accurate than they intended.
Bitter orange (also called Seville orange and sour orange) is touted as an energy-enhancing fat burner, boosting the metabolism and exercise endurance, as was ephedrine. There is some evidence that, like ephedrine, it may cause slightly more weight loss than diet and exercise alone. Like ephedrine, it is frequently blended in formulations with large doses of caffeine.
And the active ingredients in bitter orange extract -- synephrine and octopamine -- are related to ephedrine. Synephrine was used in Europe for 30 years as a treatment for mild asthma. As a result, says State University of New York at Stony Brook microbiologist Dr. Arthur Grollman, a large body of evidence indicates that synephrine raises heart rate and blood pressure, which can lead to heart attack and stroke.
A small study by UC San Francisco researchers tested two products that contained bitter orange extracts -- Advantra Z and Xenadrine EFX -- on 10 healthy adults. Their findings, published in September 2005 in the American Journal of Medicine, found that single doses of both products boosted heart rates 11 to 16 beats per minute over normal baseline heart rates.
The NIH's National Center for Complementary and Alternative Medicine says there "have been reports of fainting, heart attack and stroke in healthy people after taking bitter orange supplements alone or combined with caffeine." It adds, "there is currently little evidence that bitter orange is safer to use than ephedra."