Some Dietary Ingredients for Weight-loss:
Presumed Mechanisms, Safety and Efficacy

Mechanism, Safety, Efficacy


Suppresses appetite, increases energy

Hoodia contains a chemical constituent known as “p57” which is supposed to be the active ingredient in appetite suppression. P57 was patented by a company in England called Phytopharm, LTD, who then licensed it to Pfizer. Pfizer dropped the product after early trials, for vague reasons. Reports later circulated that the levels of Hoodia required to suppress appetite in rats and dogs was extremely large and produced severe liver damage. It may have also caused kidney damage. Whatever the actual reason, if it had worked at all, they would have developed it, as a viable weight-loss drug would be a verifiable gold mine for any drug company.

Green Tea

Burns Fat

Green tea contains polyphenolic antioxidants and limited amounts of caffeine. While some animal studies have demonstrated small increases in metabolism, there have been no studies actually demonstrating weight-loss in individuals with excess weight or obesity. One small study of 10 patients did find increased 24-hour energy expenditure and fat oxidation, but did not look at weight-loss. On the positive side, green tea is high in antioxidants, and is considered to be quite safe. It should not be used by those with heart or liver disease, pregnant or nursing women unless advised by a doctor. Anyone sensitive to caffeine should also be cautious about green tea use, though the caffeine content is quite low.Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, 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;70:1040-5.


Block fat absorption

Also called chitin, this is an extract from the shells of crustaceans like shrimp and lobster. Chitin is not absorbed by the body. Rather it forms a gel in the intestine. While limited study shows that this gel can bind cholesterol, fats soluble vitamins (A, E, D and K), calcium, and some fats in the gut, studies have not demonstrated an over all change in fat excretion or absorption. One meta-analysis of human trials did show an increased weight-loss of about seven pounds over placebo, however other studies have failed to support this. There is some support for chitosan lowering cholesterol, although trials are very limited. There have been warnings from the FDA to manufacturers of Chitosan products for making false product claims. Chitosan is not absorbed by the body, which does make it relatively safe. Because it comes from shellfish, those with shellfish allergy should avoid it. As it also binds to calcium and fat-soluble vitamins, use in pregnancy, breast feeding or by those with nutritional concerns should be avoided. It can also cause digestive problems including gas and constipation.

Ernst E, Pittler MH. Chitosan as a treatment for body weight reduction? A meta-analysis. Perfusion 1998;11:461-5.
Pittler MH, Abbot NC, Harkness EF, Ernst E. Randomized, double-blind trial of chitosan for body weight reduction. Eur J Clin Nutr 1999;53:379-81.
Maezaki Y, et al. Hypocholesterolemic effect of chitosan in adult males. Biosci Biotech Biochem 1993;57:1439-44.

White Kidney Bean Extract

Block carbohydrate absorption, called “starch blockers”

Kidney beans and a few other foods contain substances that inhibit the enzyme alpha-amylase, which digests some carbohydrates. These products were very popular about 20 years ago and had a recent resurgence with the rise of low carb diets. It is interesting to note that in the 1980s the FDA actually shut down many companies making these products, but under new regulations like DSHEA, they were allowed to re-emerge. In the past couple of years, the FDA has been busy once again sending warning letters to companies manufacturing and marketing “starch blockers.” The science also does not appear to hold up. While the ingredient may be able to inhibit some enzyme function in lab studies, human trials have shown no effect at all. The safety of these products has also been questioned, especially for diabetics. Carlson, G., Li, B., Bass, P, Olsen, W. (1983). A bean alpha-amylase inhibitor formulation (starch blocker) is ineffective in man. Science 219: 393-395

Bo-Linn GW, Morawski SG, Fordtran JS. Starch blockers–their effect on calorie absorption from a high-starch meal. NEJM 1982; 307:1413-1416.

Yerba Mate/Guarana (caffeine)

Increase metabolism/Burns fat

Yerba Mate and Guarna are both caffeine containing herbs which have seen increased popularity since the Ephedra ban. They do not contain ephedra alkaloids. All reported claims are based on the functions of caffeine. Caffeine is a central nervous system stimulant. Caffeine also increases metabolism and acts as a diuretic. This said, caffeine, even at doses that would really give you the jitters, has never been shown to produce significant weight-loss. One study of 18,417 men and 39,740 women over 12 years did show that those who used 100mg of caffeine regularly gained less weight than those who used less. One study using a combination of these two herbs in 47 overweight patients did demonstrate increased satiety and delayed gastric emptying, and very small, but not significant weight-loss. Overall, there is just not substantial evidence for caffeine impacting body weight. All caffeine can result in anxiety, insomnia, tremor and palpitations. If you really want caffeine, coffee (with about 75 mg per cup) may be less exotic, but can be had for a lot less money.

Dulloo AG, Geissler CA, Horton T, Collins A, Miller DS. Normal caffeine consumption: influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers. Am J Clin Nutr 1989;49:44–50.
Andersen T, Fogh J. Weight-loss and delayed gastric emptying following a South American herbal preparation in overweight patients.
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Regulates blood sugar, promotes weight-loss, increased muscle mass

Chromium is an essential trace element involved in the regulation of blood glucose by enhancing the action of insulin at the insulin receptor. In deficiency states, abnormal insulin response, glucose metabolism and blood lipids are seen. At least a dozen studies have looked at the relationship between chromium supplementation and body composition in humans, most without significant results. For fat loss, a few studies have shown small, mostly statistically insignificant weight-loss with chromium supplementation. On the up side, there is some evidence that chromium can improve blood sugar and insulin regulation in diabetics, and it appears to lower LDL cholesterol in those with high LDL. As an essential nutrient, chromium is very safe at levels up to the Daily Value of 120 mcg, and here is good evidence that levels up to 400 mcg per day are quite safe. There have been a few reports of kidney damage in very high-dose (1000 mcg or more), long-term (3 months or longer) supplementation. Individuals taking insulin or medications to lower blood sugar should be careful as theoretically chromium may have an additive effect.

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Trent LK, Thieding-Cancel D. Effects of chromium picolinate on body composition. J Sports Med Phys Fitness. 1995 Dec;35(4):273-80.
Bahadori B, Wallner S, Schneider H, Wascher TC, Toplak H. Effect of chromium yeast and chromium picolinate on body composition of obese, non-diabetic patients during and after a formula diet. Acta Med Austria Ca. 1997;24:185–187.
Anderson R. Chromium, glucose intolerance and diabetes. J Amer Coll Nutr. 1998;17:548-555.
Anderson R. Elevated intake of supplemental chromium improved glucose and insulin variables in individuals with type 2 diabetes. Diabetes. 1997;46:1786-1791.
Press RI, Geller J, Evans GW. The effect of chromium picolinate on serum cholesterol and apolipoprotein fractions in human subjects.
West J Med. 1990 Jan;152(1):41-5.

Hydroxycitrate (Garcinia cambogia, HCA)

Suppress appetite, promote weight-loss

Hydroxycitrate is an extract from the Indian tamarind fruit that has been promoted for weight-loss. It has been suggested that the primary mechanism is through increasing brain serotonin, and decreasing appetite. Most studies have been done in animals, but there are a few in humans, and some have been positive for both reduced calorie intake and weight-loss. One 12-week trial in 135 patients did not produce significant results. However, another 12 week trial in 89 patients did product a small weight-loss (just under 3 pounds) compared to placebo. Participant taking the hydroxycitrate also lost slightly more body fat – but neither result was statistically significant. Safety assessments are limited to some animal data and reported side effects from clinical trials, but there are no glaring adverse events. It is noteworthy that back in the mid-1990s hydroxycitrate was being researched by Roche as a weight-loss drug, but never made it past animal trials. Again, if it looked really effective, it’s hard to believe a pharmaceutical company wouldn’t develop it.

Mattes RD, Bormann L. Effects of (-)-hydroxycitric acid on appetitive variables. Physiol Behav 2000;71:87-94
Ohia SE, Opere CA, LeDay AM, Bagchi M, Bagchi D, Stohs SJ. Safety and mechanism of appetite suppression by a novel hydroxycitric acid extract (HCA-SX). Mol Cell Biochem. 2002 Sep;238(1-2):89-103.
Greenwood MRC, Cleary MP, Gruen R, et al. Effect of (-)-hydroxycitrate on development of obesity in the Zucker obese rat. Am J Physiol 1981;240:E72–8.


Improve thyroid function, stimulate metabolism

Kelp (Laminaria species) is often found in multi-ingredient weight-loss products. Kelp contains variable levels of iodine which is a part of thyroid hormones, and thyroid hormones are important for metabolism. However, in the absence of an iodine deficiency, there is no evidence that additional iodine will improve thyroid function or metabolism. Conversely, excessive iodine may suppress thyroid function. Some kelp products have been shown to have as much as 1000 mcg of iodine – nearly seven times the RDA. Ultimately, there is no support for weight-loss. Those with thyroid disease or iodine allergy should be careful of supplements containing kelp.

5-HTP, Tryptophan

Suppress Appetite

Tryptophan and 5-hydroxytryptophan (5-HTP) are both amino acid precursors to the neurotransmitter serotonin. Low tryptophan and low serotonin have been linked to overeating, cravings and weight gain. Small trials have shown some promise, but large scale trails are really wanting. A 12-week study did show 11 pound weight-loss over placebo, along with decreased food intake. Another study of 28 women with obesity had similar results. Clinical trials have shown side effects including fatigue, nausea and headache. There have been concerns about a contaminant known as “Peak X” in tryptophan and 5-HTP supplements. A number of years ago, this resulted in a temporary ban of all products. For this reason, anyone purchasing these products should be sure to obtain them from a reputable manufacturer. Tryptophan and 5-HTP should not be taken with any medications that modify serotonin including anti-depressants, migraine medications, and some weight-loss drugs. Those with autoimmune disease, anxiety, liver disease as well and pregnant and breast feeding women should not take these products.

Ceci F, Cangiano C, Cairella M, et al. The effects of oral 5-hydroxytryptophan administration on feeding behavior in obese adult female subjects.J Neural Transm 1989;76(2):109–17.
Cangiano C, Ceci F, Cascino A, et al. Eating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan. Am J Clin Nutr 1992;56:863–7.


Weight-loss, improved body composition

DHEA is an over-the-counter steroid hormone. In the body, it is made by the adrenal gland, and can be converted to estrogen, testosterone and other hormones. Studies on DHEA and weight-loss/body composition are really mixed. A one year trial of 15 patients with a topical cream showed no change in weight, but a significant reduction in fat mass along with increased lean body mass. A 10-week study in  teens with severe obesity showed no benefit; ditto for a small study in men with obesity. DHEA is a hormone, so the safety – and whether it should even be sold over-the-counter- really needs to be questioned. Many side effects including breast tenderness, menstrual irregularities, mood changes and acne have been reported. Moreover, as it is a precursor to other hormones, there has to be a caution regarding cancer. There is not enough knowledge in this area to make self-medication with DHEA truly risk-free.

Diamond P, Cusan L, Gomez J-L, et al. Metabolic effects of 12-month percutaneous dehydroepiandrosterone replacement therapy in postmenopausal women. J Endocrinol 1996;150:S43-50.
Vogiatzi MG, Boeck MA, Vlachopapadopoulou E, et al. Dehydroepiandrosterone in morbidly obese adolescents: effects on weight, body composition, lipids, and insulin resistance. Metabolism 1996;45:1101-15.
Usiskin KS, Butterworth S, Clore JN, et al. Lack of effect of dehydroepiandrosterone in obese men. Int J Obes 1990;14:457-63.

Conjugated Linoleic Acid (CLA)

Lose weight, burn fat, increase lean body mass

Conjugated Linoleic Acid or CLA is a conjugated or hydrogenated derivative of essential fat Linoleic Acid (LA). CLA has not been shown to cause people to lose weight, but has clearly been shown to cause loss of fat in people with excess body fat. Studies have shown that at one year, overweight people may lose up to nine percent of excess body fat, while conserving lean muscle. Other, mostly shorter, studies have largely shown similar results. One study of 40 overweight adults did show a small (2.2 pound) weight-loss compared to placebo after six months, as well as prevention of “holiday weight gain.” Studies have generally shown that side effects are similar to placebo, and include gastrointestinal upset and fatigue. However, doses greater than three grams per day (which are commonly used in studies) may produce changes in serum lipids including decreases in HDL, LDL, and total cholesterol as well as possible elevation of Lp(a), so it may be wise for those using CLA to have their blood fats monitored by a physician.

Gaullier, J-M., Halse, J., Hoye, K., Kristiansen, K., Fagertun, H., Vik, H., and Gudmundsen, O. Efficacy and safety of one-year supplementation with conjugated linoleic acid in moderate overweight. 2003, in preparation.
Twatras AC, Buchholz A, Close R, Zhang Z, Schoeller D. The role of conjugated linoleic acid in reducing body fat and preventing holiday weight gain. Int J Obes (Lond). 2006 Aug 22.