Weight-loss supplements advertised as fat blockers, appetite suppressants or body-composition changers usually have little effect especially over the long term and may even harm you, according to a new U.S. study.
Of the hundreds of products reviewed by Oregon State University researcher Melinda Manore, many were scrutinized in randomized clinical trials to prove their effectiveness, and only a few products such as green tea, fibre and low-fat dairy supplements resulted in a modest weight loss compared to placebo groups.
Manore, whose study was published in Tuesday's online International Journal of Sport Nutrition and Exercise Metabolism, also notes that most of the supplements that had any weight-loss benefit were also tested as part of a reduced-calorie diet, meaning purchasing such products usually amounted to a waste of money.
"There is no strong research evidence indicating that one specific supplement will produce significant weight loss, especially long term," her study concludes. "Some foods or supplements may complement a healthy lifestyle to produce small weight losses and/or prevent weight gain over time."
"For most people, unless you alter your diet and get daily exercise, no supplement is going to have a big impact," Manore, a professor of nutrition and exercise sciences who is on the science board for the President's Council on Fitness, Sports and Nutrition, said in a release.
In the U.S., weight-loss supplements are a $2.4-billion-a-year industry. The overall weight-loss industry in Canada and the U.S. is estimated to be worth $44 billion US.
Health Canada notes that an increasing number of Canadians are using health products for weight loss, including prescription drugs and natural health products. However, since 2007, Health Canada has issued warnings involving at least 170 weight-loss products, including the supplement Hydroxycut, which in the U.S. has been linked to at least a dozen cases of liver toxicity and one death.
Although some weight-loss supplements may provide benefits when used properly as part of a weight management program, misuse can pose serious health risks, Health Canada warns. It urges anyone considering use of weight-loss products especially people under age 18, pregnant or breastfeeding women, or those who have any medical conditions or serious diseases such as heart problems, high blood pressure or diabetes to discuss any potential risks with a health-care practitioner.
The supplements examined in Manore's study fell into these categories:
Chitosan, which blocks absorption of fat or carbohydrates.
