The weight loss supplement aisle in a local drugstore is almost overwhelming. Countless bottles hold products that promise to help you lose weight, shed fat, eat less and look better.

An Oregon State University researcher who reviewed hundreds of weight loss supplements offers some helpful knowledge: Most of them are generally ineffective. Most weight loss products prompt less than two pounds of weight loss, according to her research. And some might contain illegal or dangerous substances.

“What people want is to lose weight and maintain or increase lean tissue mass,” said Melinda Manore, a professor of nutrition and exercise sciences at OSU. “There is no evidence that any one supplement does this. And some have side effects ranging from the unpleasant, such as bloating and gas, to very serious issues, such as strokes and heart problems.”

Supplements

The growing obesity problem has increased the sales of weight loss supplements, according to Manore’s report. In 2008, 34 percent of overweight or obese individuals in the U.S. said they had tried such a product. Weight loss supplements are a $2.4 billion industry in the U.S., according to the Nutrition Business Journal.

Manore, a member of the Science Board for the President’s Council on Fitness, Sports and Nutrition, researches the effects of nutrition and exercise on health and performance. She said in an email that she gets asked about weight loss supplements all the time. So she pored over all the evidence surrounding them.

Supplements fell into four categories:

• Stimulants such as caffeine or ephedra that increase metabolism.

• Products such as chitosan that block absorption of fat or carbohydrates.

• Products such as conjugated linoleic acid that claim to change body composition by decreasing fat.

• Appetite suppressants such as soluble fiber.

What to avoid

Manore said some supplements should be avoided because of their associated health risks. She suggested shunning stimulants. “I would avoid anything with ephedra or other ephedra-like substances that are aimed at increasing weight loss.”

Ephedra is the generic term for several species of plants that contain ephedrine and similar alkaloid compounds. It increases the release of the hormones norepinephrine and epinephrine, increasing energy, heart rate, blood pressure and alertness.

For weight loss, ephedra is marketed to increase metabolism and suppress the appetite. For athletic performance, it’s marketed to increase mental sharpness and performance.

Studies have found ephedra to help with short-term weight loss, but it also stresses the cardiovascular system. To date, three deaths of athletes in college and professional sports have been attributed at in least part to ephedra.

Between 1993 and 2002, researchers reported a tenfold increase in the number of ephedra reports to poison centers, leading the U.S. Food and Drug Administration to ban ephedrine alkaloids in 2004.

That prompted manufacturers to substitute botanical extracts of the ephedra plants, which were not banned. Now, Manore said, some supplements contain the herbal form of ephedra, which she described as the plant product rather than the extraction of the active ingredient from the plant. But is the herbal form less dangerous? “No,” she said. “It can have the same effects.”

Also, the form of ephedra alkaloids that is banned in the U.S. is still available in some other countries, and supplements are widely available online. Google “ephedra weight loss supplements” and you’ll find plenty to choose from.

“If you buy your supplements from non-U.S. companies, you don’t have to follow U.S. rules. Also, the FDA does not have enough people to police the Internet,” Manore said.

Since the FDA doesn’t regulate supplement manufacturers, ephedra might also be added to supplements without the consumer’s knowledge. The FDA doesn’t evaluate the safety and efficacy of weight loss supplements before they appear on the market.

Manore also suggested dieters skip products such as chitosan that block absorption of fat or carbohydrates.

Chitosan has been studied extensively but there’s limited evidence that it significantly reduces weight. Its side effects primarily include gastrointestinal distress and flatulence.

Effective weight loss

In her research, Manore found that many products had not been studied in randomized clinical trials. And, where there was research, it didn’t tend to include exercise as part of a weight loss plan.

“I don’t know how you eliminate exercise from the equation,” Manore said. “The data is very strong that exercise is crucial to not only losing weight and preserving muscle mass, but keeping the weight off.”

A few products, such as green tea or fiber, were shown to have a modest weight loss benefit — three to four pounds — but most of those products were tested as part of a reduced calorie diet.

Fiber, especially in the context of high-fiber foods, can be useful. As for green tea, it’s the extracts that have been studied, not drinking green tea. “Also, it appears if you go on a weight loss diet, making sure you have adequate calcium may improve weight loss,” she said.

However, in green tea extracts there may be other contaminants that contribute to liver damage. Some studies have found that liver problems were more likely if the product was taken on an empty stomach.

The bottom line, Manore said, is the products are not regulated, so safety is not assured. “For most people, unless you alter your diet and get daily exercise, no supplement is going to have a big impact,” she said.

However, “You might find some effect in green tea, fiber, low-fat dairy and eating adequate protein throughout the day when you are dieting.”

The study is online in the International Journal of Sport Nutrition and Exercise Metabolism.

The skinny on

Hoodia gordonii

Hoodia gordonii, billed as an appetite suppressant, is derived from a succulent plant native to Africa. A 2011 study published in the American Journal of Clinical Nutrition said that consumption of H. gordonii created episodes of nausea and disturbances of skin sensation as well as increasing blood pressure, pulse and heart rate. It was not associated with any significant reduction in caloric intake or body weight, according to the study.

Green tea extracts

Green tea extracts are stimulants that theoretically increase metabolism and make a body burn more calories. They may have a small effect on weight loss, according to Melinda Manore’s study, but have also been associated with liver damage.

Chitosan

Chitosan, extracted from the exoskeletons of marine crustaceans, is a fat binder, hypothesized to decrease the amount of fat absorbed. According to Manore’s study, it’s generally safe but can cause gastrointestinal distress. However, it’s unlikely to produce significant weight loss.

Weight loss tips

Melinda Manore, a professor of nutrition and exercise sciences at Oregon State University and a member of the Science Board for the President’s Council on Fitness, Sports and Nutrition, offers these general guidelines for healthy ways to watch your weight:

• Do not leave the house in the morning without having a plan for dinner. Spontaneous eating often results in poorer food choices.

• If you eat out, start with a large salad with low-calorie dressing or a broth-based soup. You will feel much fuller and be less likely to eat your entire entree. Or, split your entree with a dining companion or just order an appetizer in addition to your soup or salad.

• Put vegetables in every meal possible. Shred vegetables into your pasta sauce, add them into meat or just buy lots of bags of fruits and vegetables for on-the-go eating.

• Increase your fiber. Most Americans don’t get enough. When possible, eat “wet” sources of fiber rather than dry — cooked oatmeal makes you feel fuller than a fiber cracker.

• Eat whole fruits and vegetables instead of drinking calories; eat an apple rather than drink apple juice. Look at items that seem similar and eat the one that physically takes up more space. For example, eating 100 calories of grapes rather than 100 calories of raisins will make you feel fuller.

• Eliminate processed foods. Research increasingly shows that foods that are harder to digest — high-fiber foods — have a greater effect on boosting metabolism.

‘Xtreme’ risk

The U.S. Food and Drug Administration has advised consumers not to use Slim Xtreme Herbal Slimming Capsule, a weight-loss product sold on various websites and distributed by Globe All Wellness. The company falsely claims that the product is “100% natural,” according to an FDA public notice from 2011. In February, the FDA issued a letter to the maker of SlimXtreme because it contained an active pharmaceutical ingredient that had been approved for prescription treatment of obesity and was subsequently withdrawn from the market after research showed it posed an increased risk of heart attack and stroke.

Get safety alerts

To find out if a dietary supplement has been the subject of a safety alert or recall, or to sign up for consumer updates, visit the U.S. Food and Drug Administration’s Medwatch safety alert page:

www.fda.gov/ForConsumers/ConsumerUpdates/ucm153239.htm

For a comprehensive list of dietary supplements safety information, visit: www.fda.gov/Food/DietarySupplements/Alerts/default.htm