As more people fall into the category of overweight or obese,1 many are turning to dietary supplements to support their weight-loss efforts. Since the U.S. Food and Drug Administration banned the sale of products containing ephedra in 2004 due to health risks,2 consumers are looking for safe and effective alternatives. Many products on the market promise weight loss, but their claims are largely based upon animal studies. To help you assist customers in their search for supplements that safely promote weight loss, The Natural Foods Merchandiser has reviewed products backed by clinical research.
Glucomannan is a dietary fiber from the roots of the konjac plant ( Amorphophallus konjac). As this water-soluble fiber travels through the digestive tract, it forms a highly viscous, gel-like mass that can promote feelings of fullness. 3,4 Increasing noncaloric bulk in the gastrointestinal tract is believed to induce weight loss by slowing the absorption of macronutrients and increasing satiety. 3,4,5
Glucomannan has shown promise in producing significantly greater weight loss than placebo in clinical trials.3,4,5,6,7,8 In an eight-week, randomized, double-blind, placebo-controlled study, obese women lost an average of 5.5 lbs of body weight without altering their diet or exercise patterns when they consumed 1 g glucomannan fiber with 8 oz of water three times a day, one hour before each meal; in contrast, those in the placebo group gained an average of 1.5 lbs.3
Another recent randomized, double-blind, placebo-controlled study found glucomannan effective in reducing body weight an average of 9.02 lbs in healthy but overweight men and women on calorie-controlled diets.5 In this five-week, parallel-group study, 180 participants ages 19 to 60 were divided into three groups, placed on a 1,200-calorie-per-day diet and given one of three fiber supplement regimens or placebo. The regimens for each group were 1,240 mg glucomannan or placebo; 420 mg glucomannan with 420 mg guar gum or placebo; and 4,320 mg glucomannan with 900 mg guar gum and 900 mg alginate or placebo. Subjects took six tablets three times a day 15 minutes before meals, four tablets at 3 p.m. and one daily multivitamin and mineral supplement. Patients in all three fiber groups experienced significant weight loss (8.36 lbs, 9.02 lbs and 9.68 lbs, respectively) compared with those who took placebo (5.5 lbs, 4.62 lbs and 5.94 lbs, respectively), but not compared with each other.5 Because all three fiber groups included glucomannan, it can be concluded that glucomannan appears to be effective in producing weight loss when combined with a reduced-calorie diet.
A recent review of glucomannan studies supports its ability to promote satiety and significant weight loss in overweight and obese individuals, as well as improve lipid and lipoprotein parameters and glycemic status.9
Green tea comes from the unfermented leaves of the tea plant Camellia sinensis. The main substances in green tea purported to aid weight loss are catechins10,11,12,13,14 and caffeine.15 Catechins are water-soluble, antioxidant polyphenol compounds, which mainly include epigallocatechin gallate, epigallocatechin, epicatechin gallate.10,11,13 Of these, EGCG is considered the most abundant and active.10 The caffeine in green tea is a mild stimulant that enhances alertness and increases metabolic rate.15 The catechins (especially EGCG) and caffeine in green tea extract appear to work together to increase 24-hour energy expenditure, induce thermogenesis and promote fat burning in humans without increasing heart rate or adversely affecting the cardiovascular system.10,12 However, too much caffeine in relation to catechins seems to reduce the effectiveness of green tea.16
Recent findings suggest tea catechins are helpful in reducing body weight, body mass index, waist circumference, body fat mass, visceral fat and subcutaneous fat.11,13 A 12-week, double-blind study of 35 healthy normal to overweight men, 24 to 46 years old, found the catechins in green tea extract to be significantly effective in reducing body fat. Participants ingested 11.5 oz a day of oolong tea with added green tea extract, containing either 690 mg of catechins (green tea extract group) or 22 mg of catechins (control group). They were instructed to reduce their daily caloric intake by 10 percent and refrain from consuming foods or beverages high in catechins, polyphenols or caffeine (such as green tea, wine and coffee). The green tea extract group had substantial reductions in total body weight (5.28 lbs), body fat mass (3.08 lbs), waist circumference (1.3 in), BMI (0.8) and skin-fold thickness (0.13 in). The control group had considerably fewer reductions in total BW (2.86 lbs), BFM (1.54 lbs), WC (0.63 in), BMI (0.4) and skin-fold thickness (0.05 in).11
Another 12-week, double-blind study involving 195 healthy, normal to overweight adults (98 men, 97 women, 20 to 65 years old) showed that tea catechins prompted reductions in BW and BF without changes in eating habits or physical activity. Unlike the control group (41.1 mg a day of catechins), the two catechin groups (444.3 mg a day, 665.9 mg a day) experienced significant reductions in total BW (1.1 lbs, 1.3 lbs), BMI (0.2, 0.2), WC (0.35 in, 0.31 in), total fat area (1.24 sq. in, 1.24 sq. in), visceral fat area (0.62 sq. in, 0.78 sq. in) and subcutaneous fat area (0.93 sq. in, 0.47 sq. in).13 Because both catechin groups produced comparable results, the lower dose seems to be as effective as the higher dose.
Hydroxycitric acid, or HCA, is extracted from the rind of the Garcinia cambogia fruit (also called Malabar tamarind). It reportedly promotes weight loss by increasing serotonin levels, reducing hunger and appetite and suppressing carbohydrate conversion into fat by inhibiting an enzyme called ATP-citrate lyase.17,18,19 While the supplement yielded promising results in animal research,20,21,22 human trials have had mixed results.6,7,17,18,19
A 12-week randomized, double-blind, placebo-controlled trial of 135 overweight adults (19 men, 116 women, 18 to 65 years old) on a 1,200-calorie-per-day diet concluded that taking 3,000 mg a day of Garcinia cambogia extract (1,500 mg a day of HCA) did not reduce BW or BFM any more effectively than placebo.17 However, HCA may inhibit fat synthesis and reduce BW in subjects on slightly higher calorie and carbohydrate diets in combination with physical activity.18,19An eight-week, randomized, double-blind, placebo-controlled study of 60 obese adults, 21 to 50 years old, on a 2,000-calorie-a-day diet and exercise program (30 minutes per day, five days a week) found that subjects taking 4,667 mg a day of HCA-SX (a highly bioavailable form of HCA providing 2,800 mg a day of HCA) experienced greater BW loss (9.99 lbs to 12.54 lbs) and BMI (1.72 to 2.28) compared with placebo (3.53 lbs, 0.65, respectively). Additionally, appetite and food intake decreased, fat oxidation increased and lipid profiles improved for those taking HCA.19 The difference may be due to the increased intake of HCA (2,800 mg a day vs. 1,500 mg a day), better solubility of HCA-SX or both.
Conjugated linoleic acid
Conjugated linoleic acid is a family of isomers from linoleic acid, a natural fatty acid found in ruminant meat and dairy products. Although CLA is a trans fatty acid, its trans linkages are in a conjugated system and it appears to act differently than other trans fats. Thus the FDA does not require it to be counted as a trans fat in nutritional labeling.23
CLA is purported to reduce body fat and abdominal fat, increase metabolic rate and enhance muscle growth.24,2527,28 However, CLA's effects on human body weight and composition have been inconsistent. 24,25,26,27,28,29,30 A 12-week, randomized, double-blind, placebo-controlled study of 60 overweight to obese men and women did not demonstrate significant changes in BW or BMI; yet, unlike the placebo group, the CLA groups (1.7 g, 3.4 g, 5.1 g and 6.8 g) did show a slight decrease in BFM and increase in lean body mass, possibly due to exercise.25
Similar short-term randomized, double-blind, placebo-controlled studies show CLA slightly decreases abdominal fat with no effect on BW or BMI, but may also reduce HDL cholesterol and increase lipid peroxidation.26,27 A one-year, randomized, double-blind, placebo-controlled study of 180 healthy overweight men and women, 18 to 65 years old, found that on average, CLA reduced BW (3.19 lbs), BMI (0.5), BFM (4.51 lbs), increased lean body mass (1.43 lbs) and slightly decreased HDL (0.06 mmol/L), whereas placebo produced no changes. Although participants were not on a restricted-calorie diet, subjects reported decreased food intake; some mild to moderate gastrointestinal disturbances were also noted, but adverse events did not differ significantly between groups.29
A 12-week, randomized, double-blind, placebo-controlled study of 60 abdominally obese men with dyslipidemia, 35 to 65 years old, taking 3.4 g a day of CLA (either 2.6 g purified t10c12 CLA or a CLA isomer mixture of 1.22 g t10c12 and 1.2 g c9t11) indicates that certain CLA isomers, specifically t10c12, may have a negative impact on carbohydrate and lipid metabolism by inducing insulin resistance and hyperlipidemia. While there were no significant differences between placebo or CLA groups in BW, BMI, BFM or lean body mass, both CLA groups showed decreases in HDL cholesterol.30 However, CLA isomer mixtures (1.22 g t10c12 and 1.2 g c9t11 for 12 weeks, 1.31 g t10c12 and 1.39 g c9t11 for one year) caused no significant increase in insulin resistance.29,30 Due to insufficient long-term safety data, CLA supplementation is not recommended for children, pregnant women and nursing mothers.31
Citrus aurantium (bitter orange)
Citrus aurantium is a citrus tree that produces bitter orange, a highly acidic fruit also known as sour or Seville orange. Bitter orange extract contains the stimulant synephrine, which is marketed in many "ephedra-free" weight-loss supplements as a "fat burner," an aid in increasing energy and metabolism, and as an appetite suppressant with no adverse cardiovascular effects.32,33 It is promoted as a "safe" ephedra alternative, although its weight-loss efficacy, safety and cardiovascular effects are still under debate.32,33,34,35
Synephrine is a sympathomimetic amine alkaloid chemically similar to ephedrine; it has vasoconstrictive properties and causes adrenaline-like effects (increased heart rate and blood pressure).32,33 These cardiovascular reactions are enhanced when synephrine is combined with caffeine.36 Additionally, although CA may increase short-term metabolic rate, this may not produce significant long-term weight loss.35 Currently, evidence to support CA as an effective tool for weight loss or fat loss is lacking, and its short-term and long-term safety has not been established.33
Chromium picolinate is a combination of the essential trace mineral chromium with picolinic acid. It helps the body utilize sugar by improving insulin sensitivity and aids in the breakdown of carbohydrates, proteins and fats.37,38,39 CP supposedly enhances weight loss by burning body fat, improving metabolism and increasing lean muscle mass.37,39 However, human studies have instead demonstrated insignificant weight loss and fat loss when compared with placebo.6,7,37,38,39,40
An eight-month, randomized, double-blind, placebo-controlled study of 29 obese adults (14 men, 15 women) found 1,000 mcg per day of CP significantly improved insulin sensitivity compared with placebo, but did not affect BW, abdominal fat or BMI.40 In a 12-week, randomized, double-blind, placebo-controlled study involving 44 moderately obese women, 400 mcg a day of CP produced no change in BW and insignificantly affected body composition. Percent of body fat and BFM slightly decreased, and LBM increased due to the moderately intense exercise program the participants followed.37 An eight-week, randomized, double-blind, placebo-controlled study of 110 overweight to obese adults with atypical depression (75 evaluable subjects, 52 female, 23 male) found that 600 mcg a day of CP was effective in reducing appetite and carbohydrate cravings, but not BW.41 Atypical depression is characterized by increased appetite, weight gain and carbohydrate cravings, among other symptoms that differentiate it from typical clinical depression.
Chitosan is produced from chitin, the protective structural component in the exoskeleton of crustaceans such as shrimp and crabs. It is touted as a "fat trapper," suggesting it has the ability to reduce fat absorption and promote weight loss without caloric restriction by attracting fat from the digestive system and expelling it from the body via excretion.7,42,43 However, human studies do not support this claim.6,7,42,43 Its fat-binding capabilities have been shown to be minimal. For example, in a 12-day study of 15 healthy men 21 to 38 years old who consumed 4.5 g a day of chitosan, fecal fat excretion increased by only 1.1 g a day.43 A meta-analysis of 10 RDBPC trials concluded that chitosan is ineffective in reducing human BW and may have a detrimental effect upon gastrointestinal function.6
Calcium, an essential mineral for healthy bones and teeth, may improve weight loss and abdominal fat loss by suppressing lipogenesis and stimulating lipolysis in people on reduced-calorie diets.44,45 A 24-week, randomized, placebo-controlled study of 41 healthy obese women, 18 to 60 years old, on a calorie-restricted diet (average 1,300 calories per day) found increasing calcium intake from 400 mg to 500 mg a day to 1,200 mg to 1,300 mg a day (via calcium carbonate or dairy products) reduced BW (18.92 lbs to 24.41 lbs), BFM (12.37 lbs to 15.79 lbs) and abdominal fat (6.48 lbs to 8.25 lbs). Those taking the lower calcium dosage experienced less weight and fat loss (14.55 lbs, 10.6 lbs and 3.04 lbs, respectively). While intake of dietary calcium resulted in greater weight and fat loss than that seen with calcium supplements, both caused substantial reductions in fat development and accumulation, and increased fat metabolism.44
Combined data from three 25-week RDBPC trials of 100 obese premenopausal and postmenopausal women on a 500-calorie-a-day deficit diet indicated that taking 1,000 mg a day of calcium (calcium citrate or calcium citrate malate) reduced BW (15.43 lbs) and BFM (12.13 lbs) more effectively than placebo (13.67 lbs, 9.92 lbs, respectively).46 While the differences between groups were small, calcium supplementation in combination with caloric restriction appears to have potential as a weight-loss aid.
Most of these weight-loss supplements are promoted as safe and effective ways to reduce body weight and fat. Unfortunately, promising results from animal testing do not always translate into positive outcomes in humans. More good-quality, long-term studies are needed to confirm the weight-loss claims and safety of many products promoted as weight-loss agents. While some have brought about modest weight loss in humans, they will not likely produce drastic results by themselves. To be effective, most weight-loss supplements should be used in combination with a nutritionally balanced, calorie-controlled diet and exercise program. Dietary factors, such as portion size and glycemic index, may also play a role in weight reduction. With this in mind, based on these current findings, glucomannan, green tea and calcium appear to be the safest and most effective supplement choices for supporting weight loss.
Monique N. Gilbert is a freelance writer and author of Virtues of Soy: A Practical Health Guide and Cookbook (Universal Publishers, 2001).
1. Hedley AA, et al. Prevalence of overweight and obesity among US children, adolescents, and adults, 1999?2002. JAMA 2004; 291(23):2847?50.
2. [No authors listed] FDA announces rule prohibiting sale of dietary supplements containing ephedrine alkaloids effective April 12 [FDA Statement]. US Food and Drug Administration. 2004 April 12. http://www.fda.gov/bbs/topics/NEWS/2004/NEW01050.html.
3. Walsh DE, et al. Effect of glucomannan on obese patients: a clinical study. Int J Obes. 1984;8(4):289?93.
4. Reffo GC, et al. Double-blind evaluation of glucomannan versus placebo in postinfarcted patients after cardiac rehabilitation. Curr Ther Res 1990; 47(5):753?8.
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7. Saper RB, et al. Common dietary supplements for weight loss. Am Fam Physician 2004;70(9):1731?8.
8. Biancardi G, et al. Glucomannan in the treatment of overweight patients with osteoarthrosis. Curr Ther Res 1989 Nov;46(5):908?12.
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10. Dulloo AG, et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr 1999;70(6):1040?5.
11. Nagao T, et al. Ingestion of a tea rich in catechins leads to a reduction in body fat and malondialdehyde-modified LDL in men. Am J Clin Nutr 2005;81(1):122?9.
12. Berube-Parent S, et al. Effects of encapsulated green tea and Guarana extracts containing a mixture of epigallocatechin-3-gallate and caffeine on 24 h energy expenditure and fat oxidation in men. Br J Nutr 2005;94(3):432-6.
13. Kajimoto O, et al. Tea catechins with a galloyl moietly reduce body weight and fat. J Health Sci 2005;51(2):161?71.
14. Haranda U, et al. Effects of the long-term ingestion of tea catechins on energy expenditure and dietary fat oxidation in healthy subjects. J Health Sci 2005;51(2):248?52.
15. Rumpler W, et al. Oolong tea increases metabolic rate and fat oxidation in men. J Nutr 2001;131(11):2848?52.
16. Kovacs EM, et al. Effects of green tea on weight maintenance after body-weight loss. Br J Nutr 2004;91(3):431?7.
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18. Preuss HG, et al. Efficacy of a novel, natural extract of (-)-hydroxycitric acid (HCA-SX) and a combination of HCA-SX plus niacin-bound chromium and Gymnema sylvestre extract in weight-management in human volunteers: a pilot study. Nutr Res 2004;24(1):45?58.
19. Preuss HG, et al. Effects of a natural extract of (-)-hydroxycitric acid (HCA-SX) and a combination of HCA-SX plus niacin-bound chromium and Gymnema sylvestre extract on weight loss. Diabetes Obes Metab 2004;6(3):171?80.
20. Shara M, et al. Physico-chemical properties of a novel (-)-hydroxycitric acid extract and its effect on body weight, selected organ weights, hepatic lipid peroxidation and DNA fragmentation, hematology and clinical chemistry, and histopathological changes over a period of 90 days. Mol Cell Biochem 2004;260(1?2):171?86.
21. Ohia SE, et al. Safety and mechanism of appetite suppression by a novel hydroxycitric acid extract (HCA-SX). Mol Cell Biochem 2002;238(1?2):89?103.
22. Roy S, et al. Body weight and abdominal fat gene expression profile in response to a novel hydroxycitric acid-based dietary supplement. Gene Expr 2004;11(5?6):251?62.
23. [No authors listed] Questions and Answers about Trans Fat Nutrition Labeling. US Food and Drug Administration CFSAN Office of Nutritional Products, Labeling and Dietary Supplements. 2003 July 9 [Updated 2004 Mar 3, 2004 June 25, 2005 Aug 1, 2005 Sept 6 and 2006 Jan 1].
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25. Blankson H, et al. Conjugated linoleic acid reduces body fat mass in overweight and obese humans. J Nutr 2000;130(12):2943?8.
26. Riserus U, et al. Metabolic effects of conjugated linoleic acid in humans: the Swedish experience. Am J Clin Nutr 2004;79(6 Suppl):1146S?1148S.
27. Terpstra AH. Effect of conjugated linoleic acid on body composition and plasma lipids in humans: an overview of the literature. Am J Clin Nutr 2004;79(3):352-61.
28. Larsen TM, et al. Efficacy and safety of dietary supplements containing CLA for the treatment of obesity: evidence from animal and human studies. J Lipid Res 2003;44(12):2234?41. Epub 2003 Aug 16.
29. Gaullier JM, et al. Conjugated linoleic acid supplementation for 1 y reduces body fat mass in healthy overweight humans. Am J Clin Nutr 2004 Jun;79(6):1118?25.
30. Riserus U, et al. Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome. Diabetes Care 2002 Sep;25(9):1516?21.
31. [No authors listed] Conjugated Linoleic Acid (CLA). PDR Health. Thomson Healthcare. http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/con_0077.shtml.
32. Bouchard NC, et al. Ischemic stroke associated with use of an ephedra-free dietary supplement containing synephrine. Mayo Clin Proc 2005;80(4):541?5.
33. Fugh-Berman A, Myers A. Citrus aurantium, an ingredient of dietary supplements marketed for weight loss: current status of clinical and basic research. Exp Biol Med 2004;229(8):698?704.
34. Min B, et al. Absence of QTc-interval-prolonging or hemodynamic effects of a single dose of bitter-orange extract in healthy subjects. Pharmacotherapy 2005;25(12):1719?24.
35. Gougeon R, et al. Increase in the thermic effect of food in women by adrenergic amines extracted from citrus aurantium. Obes Res 2005;13(7):1187?94.
36. Jordan S, et al. Products containing bitter orange or synephrine: suspected cardiovascular adverse reactions. CMAJ 2004 12;171(8):993?4. [www.cmaj.ca/content/vol171/issue8/]
37. Volpe SL, et al. Effect of chromium supplementation and exercise on body composition, resting metabolic rate and selected biochemical parameters in moderately obese women following an exercise program. J Am Coll Nutr 2001; 20(4):293-306.
38. Cefalu WT, Hu FB. Role of chromium in human health and in diabetes. Diabetes Care 2004;27(11):2741?51.
39. Campbell WW, et al. Effects of resistance training and chromium picolinate on body composition and skeletal muscle in older men. J Appl Physiol 1999;86(1):29?39.
40. Cefalu WT, et al. Effect of chromium picolinate on insulin sensitivity in vivo. J Trace Elem Exp Med 1999;12:71?83.
41. Docherty JP, et al. A double-blind, placebo-controlled, exploratory trial of chromium picolinate in atypical depression: effect on carbohydrate craving. J Psychiatr Pract 2005;11(5):302?14.
42. Gallaher DD, et al. A glucomannan and chitosan fiber supplement decreases plasma cholesterol and increases cholesterol excretion in overweight normocholesterolemic humans. J Am Coll Nutr 2002;21(5):428?33.
43. Gades MD, Stern JS. Chitosan supplementation and fecal fat excretion in men. Obes Res 2003;11(5):683?8.
44. Zemel MB, et al. Calcium and dairy acceleration of weight and fat loss during energy restriction in obese adults. Obes Res 2004;12(4):582?90.
45. Schrager S. Dietary calcium intake and obesity. J Am Board Fam Pract 2005;18(3):205?10.
46. Shapses SA, et al. Effect of calcium supplementation on weight and fat loss in women. J Clin Endocrinol Metab 2004;89(2):632?7.
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