Americans are an impatient bunch. We prefer a quick fix over a slow solution to our problems. And when it comes to weight loss, it's no different. Rather than endure lifestyle changes that involve sacrifice and waiting for results, many of us would rather pop a weight-loss supplement pill or endure painful injections if it means quicker, faster, better.

And there's certainly no shortage of weight loss supplements -- many of which are aggressively marketed -- including CLA (Conjugated Linoleic Acid,) L-carnitine, guarana seed powder, bena extract, konjac extract, polyglucosamine, cabbage powder, pyruvate, xanthigen, chitosan, EGCG, whey protein and hCG.

This array of weight-loss supplements is profitable; according to the market research and consulting firm Marketdata Enterprises, the herbal weight-loss supplement market was estimated at $20 billion last year.

Do Weight-Loss Supplements Work?

Weight-loss supplements may boast miraculous fat-burning and trimming properties, but there's little proof to back up most of these claims.

"There are no dietary supplements that have been shown to be effective, as well as safe long term, for weight loss," says Robert Kushner, M.D., Professor of Medicine and Clinical Director of the Northwestern Comprehensive Center on Obesity, Northwestern University Feinberg School of Medicine in Chicago.

It's important to keep in mind that supplements are not approved for effectiveness or safety by the U.S. Food and Drug Administration (FDA) under the Dietary Supplement Health and Education Act of 1994 (DSHEA.)

Kushner adds, "Dietary supplements are not held to the same standard as drugs, so it's very difficult to evaluate their effectiveness, as well as their safety. I suspect many of these supplements are safe, but safety is really determined by long-term use and careful observation. And none of these dietary supplements have been held to that standard that we see for drugs."

Beyond weight loss pills. In the case of weight-loss supplements, the only thing that is slim is the evidence that they contribute to safe and effective weight loss. However, many people believe that they have tried everything to lose weight, so weight loss supplements may appear to be their last, great hope. Yet, Kushner reports that there are other options.

"If someone says they've tried everything -- and I hear this all the time -- a lot of times what they mean is that they've tried everything on their own. It's very important that people who are obese -- a long-term, chronic condition for many people -- need support, guidance and further evaluation," says Kushner. He suggests that your healthcare provider can provide professional guidance, such as evaluating your medical conditions or medications that might promote weight gain.

So, get back to the basics as we've always known them:

1. Eat fewer calories and burn more calories by moving your body more throughout the day. Scientific evidence backs the strategy of filling up on high-volume, low-calorie foods such as vegetable soup, salads, and raw or cooked veggies.

2. Incorporate more energy-using physical movements, such as shunning drive-through eateries, taking the stairs, and standing or walking while on the phone, as well as an activity program that incorporates regular exercise, such as walking, along with strength training every week.

3. Finally, aim for seven to eight hours of sleep every night. Sleep deprivation has been linked to weight gain due to hormonal influences on satiety. Remember, there are no easy short-cuts for weight loss.

Guide to 5 Top Weight Loss Supplements

While there are dozens of supplements marketed for weight loss, EN reviewed five of the most popular on the market for their weight-loss potential.

Supplement: SENSA

Origins: SENSA is a granular product which is sprinkled on foods, contains maltodextrin, tricalcium phosphate, silica, natural and artificial flavors.

Weight-loss claims: According to the maker of SENSA, as you eat, smell and taste, receptors send messages to your brain, which releases hormones that tell your body it's time to stop eating. They call this phenomenon "sensory-specific satiety." SENSA is supposed to enhance smell and trigger our sense of feeling full so that you eat less.

Science: The founder, Allan Hirsch, M.D., F.A.C.P., has published several clinical studies showing how users lose more weight than non-users. However, the studies have not been accepted for publication in any peer-reviewed journals.

Bottom line: Skip SENSA, due to lack of published research proving its effectiveness.

Supplement: hCG (Human Chorionic Gonadotrophin)

Origins: hCG (human chorionic gonadotrophin) is a hormone produced in pregnancy.

Weight loss claims: Combined with a 500-calorie diet, hCG marketers claim that it enablers dieters to mobilize stored fat without being hungry. Available as drops, tablets, or by physician-provided injections, hCG was given a boost this year when "The Dr. Oz Show" featured an investigation on it.

Science: There's no peer-reviewed, published science to prove these claims, only testimonials. While a 500-calorie diet should result in weight loss, it's an inappropriately low level of calories without direct medical supervision.

Bottom line: Skip hCG (human chorionic gonadotrophin). Any time calories are severely restricted, nutritional inadequacies may result, according to the American Dietetic Association's Evidence Analysis Library.

3. Supplement: Xanthigen

Origins: Xanthigen is a botanical compound derived from brown seaweed and pomegranate seed oil.

Weight-loss claims: It helps premenopausal women with non-alcoholic fatty liver disease lose weight, according to the supplement makers, because when fat accumulates within the liver's cells, the liver is no longer able to regulate fat production, distribution and utilization and is linked with gradual accumulation of fat in the body. The supplement is purported to reduce liver fat, and about one week later, body weight beings to drop.

Science: A 15-week study published in 2010 in Diabetes, Obesity and Metabolism found that in 151 subjects, who took daily xanthigen supplements containing 300 mg of pomegranate seed oil plus 300 mg brown seaweed extract in addition to an 1,800-calorie diet, liver fat and body fat were reduced.

Bottom line: This product may have potential, although the research is preliminary. It's important to consider that other forms of weight loss also decrease liver and body fat. Look for future research to clarify its role in weight loss.

4. Supplement: Green Tea Extract

Origins: Green tea, rich in catechins like EGCG, comes from the Camellia sinensis plant.

Weight-loss claims: Many green tea supplements boast of their supposed fat-burning and metabolism-boosting action, which lead to weight loss.

Science: Preliminary evidence suggests that green tea extract (270 mg EGCG per day) may help reduce weight in overweight individuals who follow a reduced-calorie diet. EGCG has been shown to boost calorie burning by 50-100 calories per day.

Bottom line: It's not a miracle worker; a reduction of 50-100 calories a day probably won't make a significant impact on your weight.

5. Supplement: Stimulant laxatives, such as aloe, buckthorn, cascara, frangula, rhubarb root and senna.

Origins: Naturally-occurring botanicals long known for their laxative properties.

Weight-loss claims: Quick weight loss due to a diarrheal effect.

Science: Temporary weight loss occurs. By the time laxatives act on the large intestine, most of the calories of foods eaten have already been absorbed y the small intestine. Chronic use of laxatives can lead to dehydration, electrolyte imbalance, kidney failure and even death due to the loss of water and electrolytes.

Bottom line: Skip it. Laxatives don't promote long-term weight loss; they simply speed things up in the gastrointestinal tract.

Do Weight-Loss Supplements Work?