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Weighing in on the issue
By Dr. Barry Dworkin
Despite overwhelming evidence that weight loss strategies must incorporate proper nutrition, exercise and less calorie dense foods and intake over the long-term, many people continue to use weight-loss supplements that promise rapid results and better health.
Lifestyle changes that include balance between caloric intake and expenditure require diligent and sustained effort. Obesity’s social stigma, diet failures, quick fix claims and the “natural” aspect of the product are some of the contributing factors for supplement use.
Approximately 50 individual supplements and 125 proprietary products are on the market. The consumer must have information available to evaluate these products and come to their own conclusions.
In this review we will focus on products tested and scientifically evaluated for efficacy and safety. Unlike all prescriptions medications many supplements have not been evaluated in randomized clinical trials (RCTs).
Supplements are organized using their purported mechanism of action stateed by the manufacturer.
The Chinese and Mongolian shrub Ephedra sinica (Ma huang) contains ephedra alkaloids or adrenaline-like compounds. Adrenaline is naturally produced in our body’s adrenal glands. When secreted, it augments the metabolic rate (the body’s energy consumption rate) thus increasing energy expenditure.
Caffeine is a common ephedra product additive used to boost its stimulant effect. A review of RCTs showed that these products produced a loss of two pounds per month compared to placebo. However, long-term efficacy data is unavailable because the longest study lasted only six months.
In January 2002, Health Canada issued a voluntary recall of products containing more than eight milligrams of ephedrine per dose including combination products containing stimulants such as caffeine, and products with labels that made claims about weight loss, body-building or euphoria.
Fifty trials of ephedra were reviewed for adverse side effects; the findings indicated an estimated 2.2- to 3.6-fold increase in the odds of psychiatric, nervous system, cardiovascular, and gastrointestinal symptoms. Health Canada warns that "serious, possibly fatal, adverse effects" may occur ephedra is combined with caffeine or other stimulants.
Ephedra should not be used by people who are pregnant or lactating, those with a history of heart disease, diabetes, high blood pressure, thyroid disease, enlarged prostate, anxiety-related disorders, glaucoma or using a class of anti-depressants known as monoamine oxidase inhibitors.
Although ephedra accounted for only 0.8 per cent of all dietary supplements sales in the U.S., it caused 64 per cent of all adverse events as reported to U.S. Poison Control Centres in 2001. Ephedra remains available in Canada.
Manufacturers of chromium and ginseng supplements claim that it affects sugar and fat metabolism. There have been three small RCTs of 15 to 36 people using 200 to 400 micrograms of chromium picolinate and placebo. No differences were seen between thee groups.
There are reports that chromium picolinate doses greater than 1000 micrograms per day caused muscle destruction (rhabdomyolysis) and kidney failure. The lack of large clinical trials and unknown long-term safety profile augurs against its use.
People using ginseng versus placebo in RCTs did not show any greater weight loss.
Claims that guar gum, psyllium and glucomann increase satiety and thus reduce food intake remain unproven. Although increased fibre in the diet could theoretically absorb more water and cause a sense of early fullness, the clinical trials did not show any weight loss benefit. All three products have a good safety profile.
Hydroxycitric acid (HCA) is purported to decrease fat production by blocking an enzyme involved in fatty acid creation. HCA comes from the Indian Malabar tamarind tropical fruit (Garcinia cambogia).
Two RCTs using different formulations of HCA produced conflicting results. In the first, 89 overweight women with an average Body Mass Index (BMI) of 28.6 used 750 milligrams of HCA per day versus placebo over 12 weeks and lost 1.3 kilograms. The second study of 135 men and women with average BMIs of 31.2 using a different HCA formulation of 1500 milligrams per day was no different than placebo.
Both studies did not show any adverse side effects although the evidence for efficacy is scant.
Conjugated linoleic acid (CLA) is a trans-fatty acid that has been found to reduce fat deposition in obese mice. A 12-week RCT of 60 patients using 3.4 to 6.8 g per day of CLA reported no change in BMI. Currently, no human data support the efficacy of CLA in weight-loss products.
Green tea, licorice, pyruvate, vitamin B5, and l-carnitine have not been subjected to RCTs. There is no evidence to support their use as a weight loss supplement. Licorice has been reported to cause high blood pressure and low blood potassium levels.
Chitosan, derived from chitin found in crustacean shells, is purported to reduce fat absorption in the intestine. Three well-designed RCTs did not establish any significant weight loss but was safe to use.
In general, it is advisable to research the product by referring to reputable sources of evidence-based medical research.
References:
The Natural Medicines Comprehensive Database
E-pocrates
ConsumerLab.com
Natural Standard
Fugh-Berman A. The five-minute herb & dietary supplement consult. Philadelphia: Lippincott Williams & Wilkins, 2003
Evidence-based herbal medicine by Rotblatt M, Ziment. Philadelphia: Lippincott Williams & Wilkins, 2001.
Dr. Barry Dworkin, host of the nationally syndicated radio health show Sunday House Call is a family physician and an assistant professor of family medicine at the University of Ottawa.
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