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.”
The ingredient from which the Hydroxycut name was originally drawn is a derivative of the Malabar tamarind, or Garcinia cambogia. Used in traditional medicine to treat high cholesterol, it is touted as an agent that interferes with fat metabolism and possibly suppresses appetite. Its prospects were considered sufficiently promising that the pharmaceutical giant Hoffman-LaRoche in the 1960s committed significant funds to develop it as a possible weight-loss pill. The company dropped it, however, when rat studies showed that, at doses that appeared effective at reducing fat deposits, hydroxycitrate caused “potent testicular atrophy and toxicity.”
Conjugated linoleic acid
Frequently included in products that promise to help dieters transform fat into lean muscle mass, CLA is a polyunsaturated fat found naturally in milk and meat and derived from the oil of sunflower (Helianthus annuus) and safflower (Carthamus tinctorius) seeds. One product that touts its power -- Phosphacore -- says that Carthamus tinctorius “may work to safely break up and flush away unhealthy adipose (fat) cells.”
There’s no good evidence that that’s so in humans.
Sometimes recommended to patients with high overall cholesterol levels, CLA also appears to lower HDL (“good”) cholesterol. And while patients with diabetes were once thought to benefit from taking CLA supplements, further studies have not borne that out. In fact, there is some evidence that for obese people, taking in too much CLA can contribute to a prediabetic state. One study found that CLA can prevent some human cells from taking up glucose and fatty acids. That could increase blood sugar and lipids in the blood and raise the risk of diabetes and heart disease.
Tinctures of golden root (Rhodiola rosea) or other herbs, such as rose root, are widely marketed as weight-loss aids on the argument that stress -- which causes the release of the hormone cortisol -- can lead to weight gain and, particularly, to the accumulation of belly fat. In 2007, the Federal Trade Commission charged the marketers of two products -- CortiSlim and CortiStress, with making false and unsubstantiated claims about their product’s weight-loss properties, leading to a multimillion dollar settlement. But many products still make the claim.
There is no evidence that blocking cortisol causes weight loss, or that herbal remedies lower cortisol levels, according to the Mayo Clinic’s Katherine Zeratsky, a dietitian. In fact, the accumulation of fat due to high levels of cortisol appears to happen only in cases where there is an underlying medical issue, such as Cushing’s disease, or as a side effect of certain drugs.
Glutathione, green tea extracts and, more recently, the Brazilian acai berry are among the many sources of antioxidants marketed in supplements as an aid to weight loss. In test tubes, antioxidants called flavenoids and phenolic acids have been found to cut the production of triglycerides in mouse fat cells. But their weight-loss properties in humans haven’t been rigorously tested yet. Antioxidants are thought to reduce cell damage that can lead to cancer growth, which also leads to their widespread marketing as an aid to detoxifying diets.
Research suggests that glutathione taken orally is not well absorbed across the gastrointestinal tract. In a study in which very large doses of oral glutathione were administered to humans, researchers concluded it was not possible to increase circulating glutathione to levels that could have any clinical benefit. Extracts of green tea and the increasingly popular acai berry, at least, may differ from glutathione in that there is evidence they are taken in through the gut and do make it into the bloodstream. But whether it helps to neutralize toxins or fats once there remains an open question.
The chemically cleansed product of grinding up the shells of shrimps, crabs and lobsters, chitosan is a powder that has been used in the water-purification industry for years: Sprinkled on top of holding tanks, it binds to lipids, or fats. Fats and oils can thus be skimmed off easily. This has led to the claim that supplements containing chitosan have amazing “fat magnet” qualities, absorbing dietary fat before it can be absorbed into the gut and flushing it away. In addition, chitosan is touted as a source of fiber, which may contribute to sensations of fullness when consumed with a meal.
But does chitosan act in the body in the same way it does in water-purification plants? Three human clinical trials found no difference in weight or serum cholesterol levels between subjects taking chitosan supplements and those taking a placebo after three-to-eight weeks. While chitosan is generally considered safe, it could be dangerous to anyone with shellfish allergies.
A succulent plant native to the Kalahari Desert in Africa, hoodia (Hoodia gordonii) is chewed and eaten by San Bushmen to reduce their hunger and thirst during long hunts. This back story has raised hoodia to mythic levels in the world of weight-loss supplement marketing.
In a September 2004 study published in Brain Research, scientists injected p57, thought to be the active ingredient in hoodia, into a region of rats’ brains thought to govern appetite. They found reduced activity there.
In 1998, the drug maker Pfizer purchased the right to develop p57 for $21 million, but abandoned the quest for a hoodia drug in 2003. Unilever, which makes Slim-Fast meal-replacement products, recently dropped plans to fortify its products with hoodia. A former Pfizer scientist has warned that in extracting p57 from hoodia, researchers at Pfizer found that some components could not be removed that had “unwanted effects” on the liver. In an April 26, 2005, letter to the New York Times, scientist Jasjit S. Bindra warned that dieters “should be wary of using” hoodia until its safety has been better established.
Iovate’s voluntary recall of Hydroxycut products, notably, did not include its hoodia formulation -- an indication that the FDA has not found evidence of serious danger.
Wild ginger (Asarum canadense) is among a family of plants widely used in Chinese and traditional medicine for stomach ailments, to restore a woman’s energy after the birth of a child, to treat cough, allergy and breathing problems, and in some weight-loss formulas.
Aristolochic acid, says Grollman, “is one of the most potent human carcinogens ever known.” Declaring the substance to be both cancer-causing and toxic to human kidneys, the FDA in 2001 advised the U.S. dietary-supplements industry not to manufacture products using the chemical and banned its importation. But a 2003 letter to the FDA from UC Berkeley’s Carcinogenic Potency Project identified 112 herbal products still available online that contain, or were likely to contain, aristolochic acid.
The danger of aristolochic acid came to light when more than 100 women participating in a weight-loss program in Belgium developed kidney damage and urinary tract cancers. All had been prescribed an herbal weight-loss remedy that contained it. Though banned throughout Europe and in Japan, Aristolochia extracts continue to be used widely in China. Any product bearing the species name “Aristolochia,” “Bragantia” or “Asarum” should be avoided.