It?s no secret that obesity has reached epidemic proportions in the United States. More than 60 percent of Americans classify as overweight or obese, and the problem is prevalent in Europe and beyond. This situation makes weight loss big business. Diet books make the best-seller lists each year, and researchers diligently dig for the gene, the molecule or the medication that will provide people the help they need to lose weight and keep it off. But those who are struggling with excess weight or obesity want help now.
Being overweight or obese greatly increases the risk for such killers as heart disease, cancer and diabetes. For people who are trying to eat right and exercise but don?t want to resort to prescription medications for additional support, there are a number of supplements that promise to aid weight loss. But it?s hard to know which ones are backed by research and which ones are based on little more than hope. Here?s a rundown of what every retailer should know about some of the most popular weight-loss remedies and what researchers have discovered about their effectiveness and safety.
Chitosan is an amino polysaccharide made from the powdered shells of marine crustaceans, such as prawns and crabs.1 It is sold as a ?fat blocker? that binds to dietary fat and prevents its absorption, resulting in weight loss. Most studies have been done with animals,1 and the few clinical trials conducted have found it is ineffective at absorbing fat, affecting energy balance or helping with weight loss.2,3,4,5
Chromium is an essential mineral found in brewer?s yeast, beef and fortified cereals. The two most common forms of the supplement are niacin-bound chromium and chromium picolinate, both of which are promoted for weight loss. Chromium picolinate is by far the more researched of the two, though most studies have investigated the positive effect the supplement has on blood sugar levels and diabetes.6,7 A pilot study was designed to determine whether 600 mcg a day of niacin-bound chromium given to 20 overweight African-American women would result in weight loss. Although the weight loss findings were inconsistent, the researchers did notice a significant loss of fat and a sparing of muscle in the chromium group compared with the placebo group.8
In other studies done using chromium picolinate, researchers have found regular supplementation results in a small loss of body fat and an increase in lean body mass in a variety of population groups.9,10,11,12,13 However, in a more recent study of moderately obese women, researchers found chromium picolinate to have no effect on body composition.14 In a meta-analysis of 10 of the most well-designed studies for weight loss, researchers concluded that chromium picolinate supplementation resulted in a relatively small effect (with debatable clinical relevance) on body weight reduction.15 There are some concerns about the safety of chromium picolinate, but they are based on laboratory studies and studies with fruit flies, both using extremely large supplement doses.16,17,18 However, in rat and human studies, researchers found no chromosomal or DNA damage resulting from typical supplemental doses of the compound.19,20
Citrus aurantium (bitter orange), an extract of Seville oranges, is a source of the compound m-synephrine, an alkaloid similar in structure to ephedrine, the active component of ma huang.21 Because of reported side effects stemming from ephedra-containing weight-loss supplements use, many companies are now substituting Citrus aurantium for ephedra in their formulations. The orange extract is reported to act as a thermogenic agent, increasing the body?s ability to burn calories.22 A small unpublished study submitted as part of the patent application for Advantra Z, a Citrus aurantium product, found a 4 percent increase in the thermogenic response after a high-protein meal. But there are no published studies to show its effectiveness when used alone for a period of time. More research is needed.
Coleus forskohlii is a plant native to India that has been used in herbal medicine to treat a variety of disorders. The active ingredient is forskolin, which affects the breakdown of stored fats in animals and humans.23 However, there is little research regarding its effectiveness as a weight-loss aid in humans. The makers of ForsLean, the principal source of forskolin standardized extracts in the United States, conducted a small uncontrolled, self-published study of six overweight female volunteers who took 250 mg of a 10 percent forskolin extract twice daily for eight weeks. Participants lost an average of 7.25 pounds of body weight and showed a 7.7 percent body fat reduction.24 However, in a more recent study of 19 obese women taking 250 mg of a 10 percent forskolin extract twice a day for 12 weeks, researchers found that although the forskolin group lost only 1.31 pounds, the placebo group gained 2.8 pounds, suggesting the herbal extract may have helped prevent weight gain. There were no differences in caloric intake between the two groups.23
Conjugated linoleic acid is a polyunsaturated fatty acid that has been shown in several animal studies to reduce body fat and increase lean body mass.25 In addition, there have been several clinical trials showing significant decreases in body fat (from 2 percent to 20 percent) both in overweight and normal weight volunteers. In these studies, subjects took CLA doses ranging from 1.8 to 4.2 g daily for four to 12 weeks.25,26,27,28 The exact mechanism enabling CLA to reduce body fat hasn?t been determined, but it?s believed to act directly on fat cells, where fat is stored for energy, and muscle cells, where fat is burned for energy.
Not all results have been positive, though. In a recent study in healthy, normal adults, researchers found CLA supplementation (3 g daily) had no effect on body weight.29 In another, with resistance-trained adults, researchers also found that a 3.4 g per day CLA dose did not alter percent body fat or body weight.30 And in a group of men with abdominal obesity, supplementing with 6 g daily actually increased insulin resistance, which is a health risk for diabetes and heart disease.31 Other reports have suggested just the opposite—that CLA decreases insulin resistance. The 6 g per day dose used in the aforementioned study, however, was higher than most. Clearly, more research is needed.
Although CLA is generally considered safe, one animal study found that mice supplemented with CLA developed enlarged livers.32
Green tea has been studied extensively around the world for its health-promoting properties, such as the potential to lower cholesterol, reduce cancer risk and even as a way to regenerate dying skin cells. Researchers have recently discovered that an extract of green tea has thermogenic effects on the body, meaning it increases the number of calories burned and promotes fat oxidation (burning fat tissue for energy).
Green tea is a rich source of antioxidants, mainly in the form of catechins, which are naturally occurring phytonutrients found in the tea leaves. Researchers believe these phytonutrients may play a role in controlling body composition and aiding weight loss.33 In one study performed in Switzerland, 10 healthy men were given green tea extract with caffeine, caffeine alone or a placebo on three different days.34 The treatment group received a total of 275 mg of catechins and 150 mg of caffeine a day. Each day, the men were fed breakfast, lunch and dinner, and the number of calories they burned was measured. Their calorie intake and the nutrient composition of their diets, as well as their patterns of physical activity, were not altered during the study. The researchers found when the subjects were given the green tea extract there was a significant increase (4 percent) in the amount of calories burned compared with either the caffeine alone or the placebo. The researchers suggest green tea increases thermogenesis via its catechin content, since the increase was more than was seen with caffeine alone. More research is needed to confirm these findings.
Hydroxycitric acid is a natural extract from the Garcinia cambogia plant. It is reported to work by inhibiting the body?s fat production and reducing appetite.35,36 Animal studies have shown HCA suppresses fat production and reduces food intake, resulting in weight loss.37,38 Human trials, however, have not been as promising. Although HCA has been researched repeatedly and found to be safe,39 there is little convincing evidence it is an effective weight-loss aid. Results of most studies show HCA supplementation does not affect fat production, calories burned or body composition.40,41,42,43,44 However, the data is mixed?results of some studies do suggest HCA supplements reduce calorie intake,36 possibly by affecting satiety, and result in greater weight loss than placebo.45
L-carnitine is an amino acid found in meat and dairy products. It occurs naturally in the body and is essential for converting fat to energy. Several animal studies suggest L-carnitine supplementation can influence fat metabolism and affect body composition.46 To date, however, there is little evidence showing L-carnitine is of any value for weight loss in humans.47 Results of a recent trial involving 36 moderately overweight premenopausal women suggested no benefit. These women supplemented with 2 g of L-carnitine twice daily for eight weeks. They also walked 30 minutes at about 60 percent to 70 percent of maximum heart rate four days a week. The L-carnitine supplementation did not significantly improve the subjects? lean body mass or resting energy expenditure. Additionally, five of the subjects taking the L-carnitine supplements experienced nausea or diarrhea and did not complete the study.48 In another study, researchers found 1 g of L-carnitine taken three times a day by healthy adults resulted in increased fat oxidation. However, weight loss wasn?t measured.49
Starch blockers have been around for years, reaching a popularity peak almost two decades ago. They are said to aid weight loss by inhibiting the starch-digesting enzyme alpha amylase before it can convert starch into glucose, which is then converted to fat. Researchers have shown one wheat-based amylase-inhibitor did indeed stanch the starch-digesting enzyme in humans.50 Starch blockers are also said to extend the feeling of fullness and reduce food intake. However, there is little published research on the effectiveness of starch blockers as weight-loss aids. One rat study, performed more than a decade ago, found a soybean starch blocker did not promote weight loss.51 There are several unpublished studies performed for Pharmachem, the maker of a starch blocker extracted from white kidney beans and used as an ingredient in several popular weight-loss supplements. These studies have almost unanimously found their product, Phase 2, to be an effective weight loss aid.52 But one might assume some bias on the manufacturer?s part.
YGD, a combination of yerba mat? (leaves of Ilex paraguaiensis), guarana (seeds of Paullinia cupana), and damiana (leaves of Turnera diffusa or T. aphrodisiaca), is believed to act as a weight-loss aid by increasing satiation and reducing calorie consumption. The combo has been the subject of only one published study, conducted by Danish researchers.53 In the study, involving 47 healthy overweight patients, researchers found those who took three YGD tablets, each containing 112 mg yerba mat?, 95 mg guarana and 36 mg damiana extract, before each meal for 45 days had a significant delay in stomach emptying, experienced a shorter time to feel full and had a significant weight loss compared with the placebo group—1.75 pounds compared with 0.66 pounds. There was no further weight loss, however, in 22 patients who completed a 12-month maintenance treatment with YGD. No dietary advice was given during the study or maintenance period.
Despite the popularity of weight loss supplements—and the prevalence of health problems associated with overweight and obesity—there is surprisingly little definitive research on product effectiveness. Of the supplements covered here, chromium picolinate and conjugated linoleic acid are the most studied. Although in some studies researchers found them to promote weight or fat loss, neither has been conclusively proven to be an effective weight loss aid. Green tea extract has had intriguing initial research findings, but more studies are needed to evaluate the effectiveness.
Densie Webb Ph.D., R.D., is a freelance writer and editor specializing in health and nutrition. Her latest book, The Dish on Eating Healthy and Being Fabulous (Atria Books) is due out in May 2004.
1. The Medical Journal of Australia. www.mja.com/au.
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50. Choudhury A, et al. Character of a wheat amylase inhibitor preparation and effects of fasting human pancreaticobiliary secretions and hormones. Gastroenterology 1996 Nov;111(5):1313-20.
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52. Pharmachem, www.starchstopper.com/study.
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