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Do appetite suppressants work?

Appetite suppressants are meant to decrease your appetite so you are able to eat fewer calories and thus lose weight. Below we detail a variety of appetite suppressants, including potato extract, hydroxycitric acid (HCA) (Garcinia cambogia), caralluma, hoodia, glucomannan, guar gum and 5-hydroxytryptophan (5-HTP).

Potato extract

What is it? Potato extract is a purified protein extract taken from potatoes (Solanum tuberosum) sometimes referred to as PI2. It is the main ingredient found in the supplement Slendesta, made by Kemin Industries, Inc., and the claim is that it suppresses appetite by increasing the effects of cholecystokinin (CCK), a hormone involved in digestion that helps to make you feel full.

Does it work? Considering that a search for clinical studies examining potato extract comes up empty, there is no evidence to suggest it would aid weight loss efforts.

Is potato extract safe? Though safe when consumed for food, it is unknown whether potato extract has any side effects, or unintended consequences, when used as a supplement.

Hydroxycitric acid (HCA) (Garcinia cambogia)

What is it? Hydroxycitric acid (HCA) is the active ingredient of the Malabar tamarind (Garcinia cambogia), a tropical fruit found in South and Southeast Asia. It is purported to suppress appetite, increase exercise tolerance and inhibit the production of fatty acids in the body.

Does it work? It's unclear whether using HCA increases weight loss and suppresses appetite, because the research is contradictory. Some clinical studies have shown a modest weight loss over time with the use of HCA, and an equal number of studies have shown no weight loss. At this point more research is needed.

Is hydroxycitric acid safe? When used for short periods, HCA is likely safe, but there in insufficient evidence to determine the safety of using HCA for long periods of time. Adverse events, or unintended consequences, reported in some studies with the use of HCA include: headache, nausea and stomach pain.

In 2009, the Food and Drug Administration (FDA) issued a warning on Hydroxycut products, made by lovate Health Sciences Research Inc., which contained Garcinia cambogia. The warning was due to 23 reports of various levels of liver damage; one person required a liver transplant. Hydroxycut contains multiple ingredients and it is unclear whether Garcinia cambogia alone or in interaction with the other ingredients was the cause of the liver damage. The manufacturers of Hydroxycut recalled and reformulated their products, and they removed Garcinia cambogia from all of them.

Caralluma (Caralluma fimbriata)

What is it? Caralluma (Caralluma fimbriata) is known as a "famine food," because the native populations of India use the edible cactus to suppress hunger. It is the main ingredient of the product Slimaluma, made by Gencor Pacific.

Does it work? It's promising. A preliminary study conducted with rats showed that caralluma caused a significant decrease in food intake, body weight and body fat. Though this is promising, there is no guarantee that similar results will occur with humans. One clinical study conducted with humans was published in the May 2007 issue of the journal, Appetite. It found that caralluma use for two months significantly decreased appetite and waist circumference compared to a placebo. What's more: Some weight loss occurred with caralluma, but it was not statistically significant. It will be interesting to see what more research uncovers.

Is caralluma safe? Caralluma appears to be safe when taken for short periods. Reported side effects include abdominal bloating, gas, constipation and stomach irritation, though these subsided after the first week of use. Because of limited safety information, it is not known if caralluma interacts with any other supplements or medications.

Hoodia (Hoodia gordonii)

What is it? Hoodia, or hoodia gordonii, is a cactus native to the Kalahari Desert is southern Africa. "Kalahari Bushmen have traditionally eaten hoodia stems to reduce their hunger and thirst during long hunts," according to the National Center for Complementary and Alternative Medicine (NCCAM), and this fact caught the attention of the diet industry.

Does it work? Possibly. While numerous studies have been conducted on the chemical content of hoodia to determine what may be responsible for its purported appetite suppression capabilities, no clinical studies have been done to determine if hoodia does suppress appetite or cause weight loss. The anecdotal evidence from the Kalahari Bushmen is important, but more clinical research is needed.

Is hoodia safe? There have been no reports of adverse events, or unintended consequences, of taking hoodia, but neither has it been rigorously studied. According to NCCAM, the quality of hoodia products varies widely, so if you choose to take a supplement with hoodia, research it thoroughly first.

Glucomannan (Amorphophallus konjac)

What is it? Glucomannan is a fiber made from the root of Amorphophallus konjac, also known simply as konjac. It is a plant native to eastern Asia and is commonly used to make gelatins. Glucomannan is used in the US as a thickening agent. The chemical structure of glucomannan is similar to that of another appetite suppressant, guar gum.

Does it work? Possibly, but more research is needed. Glucomannan is purported to work by absorbing water and increasing in size, and thereby creating a sense of fullness since it can't be absorbed by the body. Some studies have shown a modest amount of weight loss with the use of glucomannan, but these have been small.

Is glucomannan safe? Possibly not. While few side effects have been reported with the use of glucomannan, those that have are serious. Esophageal and gastrointestinal obstructions have been linked to consuming glucomannan in tablet form; because of that, glucomannan in powder or capsule form is preferred. If you have any history of gastrointestinal obstruction, you should avoid taking glucomannan altogether. It has also been reported to lower blood glucose and should be taken with caution by diabetics. Glucomannan can also potentially interfere with the absorption of some medications. If you are diabetic, have a history of inflammatory bowel disease or are on any medications, speak to your healthcare provider prior to taking any glucomannan supplement.

Guar gum

What is it? Guar gum is a dietary fiber composed of galactomannan that is made from the seeds of the guar bean (Cyamopsis tetragonolobus). In small amounts, it is used as a thickening agent for foods and medications. When immersed in water, guar gum is capable of swelling to 10 to 20 times its size, and this is believed to create the sense of fullness that helps users to eat less.

Does it work? No. Numerous clinical studies have found guar gum be ineffective with no significant weight loss was associated with its use.

Is guar gum safe? Guar gum has been "generally recognized as safe" (GRAS) by the Food and Drug Administration (FDA) when used in small amounts. However it has some side effects, including diarrhea and gas. Taking large amounts of guar gum potentially can be dangerous as it can cause esophageal and gastrointestinal obstruction if not taken with an adequate amount of fluid -- at least 1 cup of water. If you have a history of gastrointestinal obstruction, you should avoid taking a guar gum supplement. Guar gum interacts with some medications; specifically, it interferes with the absorption of estrogens, Glucophage (metformin) and penicillin. Guar gum can also lower blood sugar and should be taken with caution by diabetics. Speak to your doctor prior to taking products with guar gum.

5-Hydroxytryptophan (5-HTP)

What is it? 5-Hydroxytryptophan (5-HTP) is also known as oxitriptan and is chemically related to L-tryptophan and serotonin. It has been used for treating depression and fibromyalgia, as well as a variety of other ailments.

Does it work? Possibly, but more research is needed. Preliminary research suggests 5-HTP may help reduce appetite and as a result decrease weight.

Is 5-HTP safe? Avoidance is best. There are a lot of concerns about the safety of taking 5-HTP as a supplement. Minor side effects, or unintended consequences, of 5-HTP use include: nausea, vomiting, heartburn, diarrhea, gas, belching and stomach pain. Some believe it may cause eosinophilia myalgia syndrome (EMS), a condition that affects certain types of blood cells and muscles, but it is unclear if the cases of EMS that have occurred are due to 5-HTP or a contaminant. Because of the severity of EMS, using 5-HTP as a supplement should be avoided until more research is completed.

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