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.
Caffeine
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.
