Losing weight can be a lifelong challenge. Researchers who study obesity consider it a chronic health condition that must be managed much like high blood pressure or high cholesterol. That means there's no easy cure.

Losing just 5% to 10% of your total weight can lower blood pressure , improve cholesterol profile, prevent diabetes , improve blood sugar control if you already have diabetes, and reduce the risk of developing osteoarthritis of the knee. 1-6

A combination of improved diet and regular exercise might be the best way to lose weight and keep it off.

Although prior weight-loss drugs, such as amphetamines and fen-phen, have had a patchy safety record, sibutramine (Meridia) appears to be safe and modestly effective for weight loss. New drugs currently in development will likely offer greater benefits.

It is commonly stated that the high-fructose corn syrup added to many foods is a major cause of obesity. However, while there is little doubt that, in general, excess intake of calories promotes obesity, the specific relationship of this substance to weight gain remains questionable. 210

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Principal Proposed Natural Treatments  

Chromium  

Chromium is a mineral the body needs in only small amounts, but it's important to human nutrition.

Although it has principally been studied for improving blood sugar control in people with diabetes , chromium has also been tried for reducing total weight and body fat percentage, with some success. Both of these potential benefits involve chromium's effects on insulin. Before we can explain how chromium may help, we need to provide some background information on how the body controls its blood sugar levels.

The body needs a constant level of glucose (sugar) in the blood. When you digest a carbohydrate meal, glucose levels rise. Protein meals have the same effect, although to a lesser extent. Your body responds by secreting insulin. Insulin causes the cells of your body to absorb glucose out of the blood, thereby reducing circulating blood sugar.

Once cells have taken in glucose, they can burn it for energy or convert it to a storage form. Liver and muscle cells can store a limited amount of glucose as glycogen. Fat cells can convert unlimited amounts of glucose into energy stored as fat.

The process also goes the opposite way. When your body has used up the food from its last meal, blood glucose levels drop. Just as the body doesn't like it when glucose levels are too high, low glucose levels also cause problems. So your body applies its control mechanisms to raise blood sugar levels. It does so by reducing its output of insulin and also by raising levels of another hormone called glucagon. The net effect is that energy storage depots are mobilized. Glycogen is converted back into glucose. In addition, fat cells release their contents into the bloodstream to supply an alternate energy source.

In summary, high insulin levels build fat, while low insulin levels break down fat.

Based on this push-pull effect, if you want to lose weight you'd probably rather keep your insulin levels low.

Dieting is the most obvious method of reducing insulin. When you don't take in enough calories to supply your body's daily needs, insulin levels fall and your body breaks down fat cells. Exercising is another method; by increasing your body's energy requirements, exercise causes insulin levels to fall and fat cells to break down.

But it's difficult to consistently use more energy than you take in. Hunger takes over, and you start wanting to eat. If there were some way to trigger fat breakdown without going hungry, it would make weight loss much easier.

There's another important connection between insulin and weight to consider. Individuals who weigh too much often develop insulin resistance . In this condition, certain cells of the body become less sensitive to insulin. The body senses this, and increases insulin production until it overcomes the resistance. It is possible that fat cells respond to these increased levels of insulin by storing even more fat.

Chromium is thought to improve the body's responsiveness to insulin. Combining this fact with the insulin-weight connections just described, some researchers have proposed that chromium may assist in decreasing weight or improving body composition (the ratio of fatty tissue to lean tissue).

Their main argument goes like this: chromium increases insulin sensitivity. This causes levels of insulin to fall. 88 With reduced amounts of insulin in the blood, fat cells are less inclined to store fat, and weight loss may become easier.

In addition, there is some evidence that chromium partially blocks insulin's effects on fat cells, interfering with its fat-building effect. 89 This could also promote weight loss. And another small study suggests that chromium may work by influencing the brain and its role in appetite and food cravings. 242

There are several flaws in these arguments, though. For example, even very small amounts of insulin in the blood effectively suppress fat breakdown. 90-94 Another problem is that during insulin resistance, fat cells also appear to become resistant to insulin. 95-98 Insulin resistance, in other words, might be a natural method of keeping the lid on weight gain. Chromium supplements might have the undesired effect of increasing the ability of fat cells to respond to insulin, helping them store fat better!

However, theory only takes one so far. It is more important to review the results of studies in which people were given chromium supplements to reduce their weight.

What Is the Scientific Evidence That Chromium Aids Weight Loss?  

About ten reasonably well designed double-blind, placebo-controlled trials have evaluated chromium’s potential benefit for weight loss. 138

In the largest study, 219 people were given either placebo , 200 mcg of chromium picolinate daily, or 400 mcg of chromium picolinate daily. 7 Participants were not advised to follow any particular diet. Over a period of 72 days, individuals taking chromium experienced significantly greater weight loss than those not taking chromium, over 2-½ pounds versus about ¼ pound. Interestingly, individuals taking chromium actually gained lean body mass, so the difference in loss of fatty tissue was greater: over 4 pounds versus less than ½ pound. However, a very high dropout rate makes the results of this study somewhat unreliable.

In a smaller double-blind study by the same researcher, 130 moderately overweight individuals attempting to lose weight were given either placebo or 400 mcg of chromium daily. 8 Although hints of benefit were seen, they were too slight to be statistically significant .

Several other small double-blind, placebo-controlled studies also failed to find evidence of the benefit of chromium picolinate as an aid to weight loss. 9-14,99,136, 211,243 One study failed to find benefit with a combination of chromium and conjugated linoleic acid . 225

When larger studies find positive results and smaller studies do not, it often indicates that the treatment under study is only weakly effective. This may be the case with chromium as a weight-loss treatment. 138

For more information, including dosage and safety issues, see the full Chromium article.

Pyruvate  

Pyruvate supplies the body with pyruvic acid, a natural compound that plays important roles in the manufacture and use of energy. Theoretically, taking pyruvate might increase the body's metabolism, particularly of fat.

Several small studies enrolling a total of about 150 people have found evidence that pyruvate or DHAP (a combination of pyruvate and the related substance dihydroxyacetone) can aid weight loss and/or improve body composition. 21-25,115

For example, in a 6-week, double-blind, placebo-controlled trial, 51 people were given either pyruvate (6 g daily), placebo, or no treatment. 115 All participated in an exercise program. In the treated group, significant decreases in fat mass (2.1 kg) and percentage body fat (2.6%) were seen, along with a significant increase in muscle mass (1.5 kg). No significant changes were seen in the placebo or nontreatment groups.

Another placebo-controlled study (blinding not stated) used a much higher dose of pyruvate, 22 g to 44 g daily depending on total calorie intake. 21 In this trial, 34 slightly overweight people were put on a mildly weight-reducing diet for 4 weeks. Subsequently, half were given a liquid dietary supplement containing pyruvate. Over the course of 6 weeks, people in the pyruvate group lost a small amount of weight (about 1-½ pounds) while those in the placebo group did not lose weight. Most of the weight loss came from fat.

Another interesting placebo-controlled study evaluated the effects of DHAP when people who had previously lost weight increased their calorie intake. 23 Seventeen severely overweight women were put on a restricted diet as inpatients for 3 weeks, during which time they lost approximately 17 pounds. They were then given a high-calorie diet. Approximately half of the women also received 15 g of pyruvate and 75 g of dihydroxyacetone daily. The results found that after 3 weeks of this weight-gaining diet, individuals receiving the supplements gained only about 4 pounds, as compared to about 6 pounds in the placebo group. Close evaluation showed that pyruvate specifically blocked regain of fat weight.

While all these studies are intriguing, we really need large studies (100 participants or more) to establish the benefits of pyruvate for weight loss.

For more information, including dosage and safety issues, see the full Pyruvate article.

Fiber  

Dietary fiber is important to many intestinal tract functions including digestion and waste excretion. It also appears to have a mild cholesterol-lowering effect and might help reduce the risk of some kinds of cancer (although the current evidence is a bit contradictory).

Fiber might also be useful for losing weight. It's thought to work in a simple way by filling the stomach and causing a feeling of fullness, while providing little to no calories. Fiber might also interfere with absorption of fat.

There are two kinds of fiber: soluble fiber, which swells up and holds water, and insoluble fiber, which does not. Soluble fiber is found in psyllium seed (sold as a laxative), apples, and oat bran. Most other plant-based foods contain insoluble fiber.

Fiber supplements may contain a variety of soluble or insoluble fibers from grain, citrus, vegetable, and even shellfish sources.

Several double-blind, placebo-controlled studies have evaluated fiber supplements as a weight-loss aid. The results have been somewhat inconsistent, but in general it appears that some forms of fiber may slightly enhance weight loss.

In one of the largest studies, 97 mildly overweight women on a strict low-calorie diet were given either placebo or an insoluble fiber (type not stated) 3 times daily for 11 weeks. 26 Women given fiber lost almost 11 pounds compared to about 7 pounds in the placebo group. Participants using the fiber reported less hunger.

Researchers weren't finished with their subjects! For an additional 16 weeks, their diet was changed to one that supplied more calories. As expected, participants regained some weight during this period. Nonetheless, by the end of the 16 weeks, individuals taking fiber were still 8 pounds lighter than at the beginning of the study, while those taking placebo were only 6 pounds lighter.

Another study evaluated whether the benefits of dietary fiber endure over 6 months of dieting. This double-blind trial of 52 overweight individuals found that use of an insoluble, dietary fiber product (made from beet, barley, and citrus) almost doubled the degree of weight loss as compared to placebo. 27 Once more, participants using the fiber supplement reported less hunger.

Two other double-blind, placebo-controlled studies evaluated a similar insoluble fiber product. 28,116 The first enrolled 60 moderately overweight women and put them on a 1,400-calorie diet along with placebo or fiber for a period of 2 months. The other study was similar, but enrolled only 45 women and followed them for 3 months. The results of both studies again showed improved weight loss and reduced feelings of hunger in the treated groups. However, a 24-week study of 53 moderately overweight individuals found no difference in effect between placebo and 4 g of insoluble fiber daily. 117 Another study failed to find benefit with either of two soluble fiber supplements (methylcellulose or pectin plus beta glucan) in terms of weight, hunger, or satiety. 149

Glucomannan , a source of soluble dietary fiber from the tubers of Amorphophallus konjac, has also been tried for weight loss, with positive results in adults. In a double-blind, placebo-controlled trial of 20 overweight individuals, researchers found that use of glucomannan significantly improved weight loss over an 8-week period. 29 Benefits were also seen in a double-blind, placebo-controlled trial of 28 overweight individuals who had just experienced a heart attack. 30 However, another trial studied the effectiveness of glucomannan as a weight-loss agent in 60 overweight children, and found no benefit. 31

An 8-week, double-blind, placebo-controlled trial of 59 overweight people evaluated the effects of chitosan , a mostly insoluble fiber from crustaceans, taken at a dose of 1.5 g prior to each of the two biggest meals of the day. 32 No special diets were assigned. The results showed that, on average, participants in the placebo group gained more than 3 pounds over the course of the study, while those taking chitosan lost more than 2 pounds. However, a subsequent 24-week, double-blind, placebo-controlled study of 250 people using the same dosage of chitosan failed to find benefit. 150 Negative results were also seen in an 8-week, double-blind, placebo-controlled trial of 51 women given 1,200 mg twice daily 118 and in a 28-day, double-blind trial of 30 overweight people using 1 g twice daily. 33 Although benefits have shown up in other studies, the balance of evidence indicate that chitosan probably does not work. 170,205,241 Further argument against the use of chitosan comes from the fact that chitosan supplements may at times contain toxic levels of arsenic. 151

A few trials have only evaluated effects on hunger and satiety rather than weight loss. One study found that the soluble fiber pectin (from apples) reduces hunger sensations. 34 Another found that the soluble fiber guar gum slows stomach emptying and increases the sensation of fullness. 35 However, a more recent study evaluated the effects of guar gum in 25 women undergoing a weight-loss program, and found no influence on hunger. 36 In another study, consuming fiber from barley caused an increase in calorie consumption. 209

Dosage  

The optimum dose of fiber and the proper time to take it have not been determined.

In the first three studies described previously, insoluble fiber supplements were given 20 to 30 minutes prior to each meal at a dose of about 2.3 g, along with a large glass of water. For additional dosage information, see the full articles on Glucomannan and Chitosan .

Safety Issues  

Fiber supplements must be taken with water; otherwise, they may block the digestive tract. Even when used properly, mild gastrointestinal side effects such as gas and bloating may occur.

As a kind of positive side effect, fiber supplements may reduce cholesterol and blood pressure levels. 37-41

For other important safety issues, see the full articles on chitosan and glucomannan .

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Other Proposed Treatments for Weight Loss  

5-hydroxytryptophan (5-HTP)  

The supplement 5-HTP is thought to affect serotonin levels. Because serotonin is thought to play a role in weight regulation, 5-HTP has been investigated as a possible weight-loss aid. A total of four small, double-blind, placebo-controlled clinical trials have been reported.

The first of these, a double-blind crossover study, found that use of 5-HTP (at a daily dose of 8 mg per kilogram body weight) reduced caloric intake despite the fact that the 19 participants made no conscious effort to eat less. 44 Participants given placebo consumed about 2,300 calories per day, while those taking 5-HTP ate only 1,800 calories daily. Use of 5-HTP appeared to lead to a significantly enhanced sense of satiety after eating. Over the course of 5 weeks, women taking 5-HTP effortlessly lost more than 3 pounds.

A follow-up study by the same research group enrolled 20 overweight women who were trying to lose weight. 45 Participants received either 5-HTP (900 mg per day) or placebo for two consecutive 6-week periods. During the first period, there was no dietary restriction, while during the second participants were encouraged to follow a defined diet expected to lead to weight loss.

Participants receiving placebo did not lose weight during either period. However, those receiving 5-HTP lost about 2% of their initial body weight during the no-diet period, and an additional 3% while on the diet. Thus, a woman with an initial weight of 170 pounds lost about 3-½ pounds after 6 weeks of using 5-HTP without dieting, and another 5 pounds while dieting. Once again, participants taking 5-HTP experienced quicker satiety.

Similar benefits were seen in a double-blind study of 14 overweight women given 900 mg of 5-HTP daily. 46

Finally, a double-blind, placebo-controlled study of 20 overweight individuals with adult-onset diabetes found that use of 5-HTP (750 mg per day) without intentional dieting resulted in about a 4-½ pound weight loss over a 2-week period. 47 Use of 5-HTP reduced carbohydrate intake by 75% and fat intake to a lesser extent.

Unfortunately, all these studies were performed by a single research group. In science, results aren't considered valid until they are independently replicated by different researchers. In addition, all these studies were small in size. For these reasons, further research is necessary before we can consider 5-HTP a proven weight-loss agent.

Garcinia cambogia  

Hydroxycitric acid (HCA) , a derivative of citric acid, is found primarily in a small, sweet, purple fruit called Garcinia cambogia , the Malabar tamarind. Although animal and test tube studies as well as one human trial suggest that HCA might encourage weight loss, other studies have found no benefit. 53-64,119,121 In an 8-week, double-blind, placebo-controlled trial of 60 overweight individuals, use of HCA at a dose of 440 mg 3 times daily produced significant weight loss as compared to placebo. 119

In contrast, a 12-week, double-blind, placebo-controlled trial of 135 overweight individuals, who were given either placebo or 500 mg of HCA 3 times daily, found no effect on body weight or fat mass. 62 However, this study has been criticized for using a high-fiber diet, which is thought to impair HCA absorption. 120

Other small placebo-controlled studies found HCA had no effect on metabolism, appetite, or weight. 63,64,121

The bottom line: It is not yet clear whether Garcinia cambogia is an effective treatment for weight loss.  

Caffeine and Ephedrine  

Caffeine and ephedrine (found in ephedra, an herb also known as ma huang) are central nervous system stimulants. Considerable evidence suggests ephedrine-caffeine combinations can modestly assist in weight loss. 65-69,135,152

For example, in a double-blind, placebo-controlled trial, 180 overweight people were placed on a weight-loss diet and given either ephedrine-caffeine (20 mg/200 mg), ephedrine alone (20 mg), caffeine alone (200 mg), or placebo, 3 times daily for 24 weeks. 70 The results showed that the ephedrine-caffeine treatment significantly enhanced weight loss, resulting in a loss of more than 36 pounds as compared to only 29 pounds in the placebo group. Neither ephedrine nor caffeine alone produced any benefit. Contrary to some reports, participants did not develop tolerance to the treatment. For the whole 6 months of the trial, the treatment group maintained the same relative weight loss advantage over the placebo group.

While this study only found benefit with caffeine-ephedrine and not with ephedrine alone, other studies have found that ephedrine alone also offers some weight loss benefits. 139

We don't know exactly how ephedrine-caffeine works. However, caffeine has actions that cause fat breakdown and enhance metabolism. 71 Ephedrine suppresses appetite and increases energy expenditure. The combination appears to produce synergistic effects, with appetite suppression probably the most important overall factor.

Note : Ephedrine presents serious medical risks, and should only be used under physician supervision. In the US, the sale of ephedrine-containing products is banned. See the full Ephedra article for more information.

Medium-Chain Triglycerides (MCTs)  

Some evidence suggests that MCT consumption might enhance the body's tendency to burn fat. 123-125,153 This has led to investigations of MCTs as a weight-loss aid. However, the results of clinical trials thus far have been fairly unimpressive.

In a 4-week, double-blind, placebo-controlled trial, 66 women were put on a very low-carbohydrate diet to induce a state called ketosis. 126 Half of the women received a liquid supplement containing ordinary fats; the other half received a similar supplement in which the ordinary fats were replaced by MCTs.

The results indicated that the MCT supplement significantly increased the rate of "fat burning" during the first 2 weeks of the trial and also reduced the loss of muscle mass. However, these benefits declined during the last 2 weeks of the trial, which suggests that the effects of MCTs are temporary.

In studies that involved substituting MCTs for ordinary fats in a low calorie diet have shown minimal relative benefits at best. 127,128,131,140,154

A related supplement called structured medium- and long-chain triacylglycerols (SMLCT) has been created to provide the same potential benefits as MCTs, but in a form that can be used as cooking oil. In a preliminary double-blind trial, SMLCT showed some promise as a “fat-burner.” 137

Other Approaches to Weight Loss  

A special type of fat known as diacylglycerol has shown promise as a weight loss aid. 80,141,142,237 For example, in a 24-week, double-blind, placebo-controlled study, 131 overweight men and women were placed on a weight loss diet including, in part, supplementary foods containing either diacylglycerols or ordinary fats. 141 The results showed that participants using diacylglycerols lost more weight. Diacylglycerols appear to be safe. 155,237

In four preliminary controlled trials, a patented, proprietary blend of fats added to yogurt has shown potential weight-loss benefit. 217-220

Korean pine nut oil (PinnoThinac), which is high in free fatty acids (FFA), was shown in one study to reduce the appetite of 42 overweight women compared to olive oil. 236

Beans partially interfere with the body's ability to digest carbohydrates, which is why they cause flatulence. Based on this, products containing the French white bean Phaseolus vulgaris have been widely marketed as weight loss aids. However, published studies studies have generally failed to find these "carbohydrate blockers" effective for this purpose. 183-185 According to the manufacturer of a current product, more concentrated extracts of phaseolus vulgaris, taken in higher doses, actually can work. Up until recently, the evidence for this claim rested entirely on unpublished studies that could not be independently verified. 186-187

In 2007, however, a relevant trial was at last published. 212 In this double-blind, placebo-controlled study, 60 slightly overweight people were given either placebo or a phaseolus extract once daily 30 minutes prior to a main meal rich in carbohydrates. Over the thirty days of the study, the results indicated that phaseolus treatment led to a significantly greater reduction of body weight and and improvement of lean/fat ratio as compared to placebo.

Some evidence suggests that the supplements creatine158 and colostrum133 may each slightly improve body composition (fat to muscle ratio) as compared to placebo among individuals undergoing an exercise program.

It has been suggested that calcium supplements, or high-calcium diets, may slightly enhance weight loss, but current evidence is more negative than positive. 147,156,171-177,219,226,230,234 However, because bones may grow thin during rapid weight loss, it may make sense to take calcium supplements when intentionally losing weight. 157 (Interestingly, when weight loss is induced by exercise rather than diet, bone loss does not seem to occur. 208 )

A 6-month, double-blind study found that the supplement DHEA at a dose of 50 mg daily may help decrease abdominal fat and improve insulin sensitivity (thereby potentially helping to prevent diabetes) in seniors. 159 However, another study failed to find DHEA at 40 mg twice daily helpful for weight loss in severely overweight adolescents. 87

A supplement related to DHEA, 3-acetyl-7-oxo-dehydroepiandrosterone (also called 7-oxy or 7-keto-DHEA), has shown a bit of promise for enhancing weight loss. 178-179

Results of two small, double-blind, placebo-controlled studies suggest that vitamin C supplements might aid in weight loss. 72,73 A related study found that marginal vitamin C deficiency might interfere with deliberate attempts to lose weight. 203

One small double-blind study indicates that a concentrated extract of the herb Coleus forskohlii might increase the rate of fat burning. 181

A double-blind, placebo-controlled trial that enrolled 158 moderately overweight volunteers tested a mixture of chromium , cayenne , inulin (a nondigestible carbohydrate), and phenylalanine (an amino acid), as well as other herbs and nutrients. 82 All participants lost weight over the 4-week trial. Those using the supplement lost a bit more weight, but the difference was not mathematically significant. However, a bit of positive news came from close examination of results. Among those taking the supplement, a significantly higher percentage of the weight loss came from fat instead of muscle.

One study found benefit with a combination treatment containing niacin-bound chromium combined with Gymnema sylvestre and HCA. 160 Yet another study reported weight-loss effects with a combination of HCA, pantothenic acid , chamomile , lavender, damask rose, and the Hawaiian herb Cananga odorata . 229

A very small study hints that soy isoflavones might help reduce buildup of abdominal fat. 215

Weight-loss benefits were seen in a double-blind trial of 150 overweight people given either placebo or one of two doses of a combination therapy containing chitosan , chromium , and HCA. 129 Benefits were also seen in a 45-day double-blind, placebo-controlled trial of 44 overweight people that tested a combination product containing yerba mate , guarana , and damiana . 130 Minimal benefits at most were seen in a 12 week double-blind study evaluating a combination of asparagus, green tea, black tea , guarana , maté , kidney beans, Garcinia cambogia, and high chromium yeast. 206

A double-blind, placebo-controlled study evaluated the effects of a mixture containing Citrus aurantium (bitter orange), caffeine, and St. John's wort . 83Citrus aurantium contains various stimulant chemicals related to nasal spray decongestants. The results suggest that this combination might assist weight loss, but the study was so small (23 participants divided into three groups) that the results mean little.

Ayurvedic herbs have shown some promise for weight loss. In a 3-month, double-blind, placebo-controlled study, 70 overweight individuals were divided into four groups: placebo, Triphala guggul (a mixture of five Ayurvedic ingredients) plus Gokshuradi guggul (a mixture of eight Ayurvedic ingredients), Triphala guggul plus Sinhanad guggul (a mixture of six Ayurvedic herbs), or Triphala guggul plus Chandraprabha vati (a mixture of 36 Ayurvedic ingredients). 143 Reportedly, all three Ayurvedic ingredients produced significant weight loss and improvements in cholesterol compared to placebo; furthermore, the improvements produced by each of the treatments were close to identical.

One study failed to find benefit with a proprietary mixture of astragalus , gallic acid, ginger , red sage, rhubarb , and turmeric . 216

Studies attempting to determine whether evening primrose oil can aid in weight loss have yielded mixed results. 74,75

One study failed to find useful results with a combination of rhubarb, ginger , astragulus , red sage, and turmeric . 182

Another study failed to find benefit with the edible cactus Caralluma fimbriata . 207

Conjugated linoleic acid (CLA) is a mixture of different isomers, or chemical forms, of linoleic acid. CLA has been proposed as a fat-burning substance, improving lean to fat mass ratios and reducing total fat mass, but, on balance, the benefit appears to be slight at best. 76-79,122,132,134,161-163,202,214,218,228,232Note: Some but not all studies have raised concerns that use of CLA by overweight people could raise insulin resistance and therefore increase risk of diabetes. 164-166,204 In addition, use of CLA might impair endothelial function and levels of C-reactive protein, and thereby increase cardiovascular risk. 191,214

One interesting study found that topical application of glycyrrhetinic acid, a constituent of licorice , can reduce fat thickness in the thigh. 192

A mixture of the herbs of Magnolia officinalis and Phellodendron amurense is said to help reduce stress-induced overeating, but the only supporting evidence for this claim is a study too small to provide meaningful results. 193

The herb Hoodia gordonii , often known simply as "hoodia," has been heavily marketed as a weight loss treatment. However, the evidence that it works is limited to one small unpublished trial funded by the manufacturer.

Hypnosis is popular as an aid to weight loss. However, a careful analysis of published studies suggests that the benefits are slight at best. 148

Although acupuncture is widely used for weight loss, as yet the evidence from published studies is incomplete and inconsistent. 144-146

One double-blind study failed to find capsaicin (the "hot" in cayenne pepper ) helpful for preventing weight regain after weight loss, but it did seem to cause some increase in fat metabolism. 167

A rather theoretical study found that two ingredients in green tea may interact to increase metabolism, 84 and on this basis green tea became a popular weight control supplement. However, other evidence indicates that if green tea increases metabolism at all, the effect is extremely small. 194-195 One study conducted in Thailand reported weight-loss benefits with green tea; 235 however, a Dutch study failed to find green tea helpful for preventing weight regain after weight loss. 168 In another study, use of green tea failed to produce significant weight loss in overweight women with polycystic ovary syndrome . 196

Green tea extract enriched with catechins (an active ingredient in green tea) has done better, enhancing weight loss in one substantial but somewhat flawed trial. 227 Oolong tea enriched with green tea catechins found some apparent weight loss benefit. 197 However, a study in overweight Japanese children did not support the effectiveness of green tea catechins for weight reduction. 238 And, similar results were obtained in another placebo-controlled trial involving 78 overweight women after 12 weeks of treatment. 239

Other supplements that have been studied but not found effective include spirulina, 81L-carnitine , 86 and oligomeric proanthocyanidin complexes (OPCs) from grape seed. 169

An enormous number of other supplements are marketed for weight loss, but without meaningful supporting evidence.

For example, certain supplements are said to be lipotropic, meaning that they help your body metabolize fat or slow down the rate at which it's stored. Vitamins B 5 and B 6 , biotin , choline , inositol , lecithin , and lipoic acid are often placed in this category. However, there is no real evidence that they'll help you lose weight.

A number of amino acids are said to reduce hunger, including phenylalanine , tyrosine , methionine , and glutamine . Because the herb kava appears to be helpful for anxiety, it has been proposed as a treatment for mood-related overeating. The antidepressant herb St. John's wort has been recommended with much the same reasoning.

Seaweeds such as kelp , bladderwrack , and sargassi are often added to diet formulas, under the assumption that they will affect the thyroid gland through their iodine content. (An underactive thyroid can cause weight gain.) However, the effect of iodine on thyroid function depends on whether you are iodine deficient. Excess iodine can actually suppress the action of the thyroid. The herb guggul ( Commiphora mukul) is often claimed to enhance thyroid function, and for this reason it is often sold as a weight-loss agent. However there is little evidence that it actually affects the thyroid, and a small double-blind trial found it no more effective than placebo for weight loss. 85

Numerous herbs and supplements with potential or known effects on insulin or blood sugar levels are widely added to weight-loss formulas, again, without any evidence that they are effective. These include:

  • Alfalfa
  • Anemarrhena asphodeloides
  • Arginine
  • Azadirachta indica ( neem )
  • Bilberry leaf
  • Bitter melon ( Momordica charantia )
  • Catharanthus roseus
  • Coccinia indica
  • Cucumis sativus
  • Cucurbita ficifolia
  • Cuminum cyminum (cumin)
  • Euphorbia prostrata
  • Garlic
  • Glucomannan
  • Guaiacum coulteri
  • Guazuma ulmifolia
  • Guggul
  • Holy basil ( Ocimum sanctum)
  • Lepechinia caulescens
  • Musa sapientum L. (banana)
  • Nopal cactus ( Opuntia streptacantha )
  • Onion
  • Psacalium peltatum
  • Pterocarpus
  • Rhizophora mangle
  • Salacia oblonga
  • Salt bush
  • Spinacea oleracea
  • Tournefortia hirsutissima
  • Turnera diffusa
  • Vanadium

Herbs with laxative or diuretic properties or reputations are also popular in weight-loss formulas, although they are unlikely to produce anything beyond a slight temporary effect. These include barberry , buchu , cascara sagrada bark, cassia powder, cleavers , cornsilk, couchgrass, dandelion root, fig, goldenrod , hydrangea root, juniper berry , peppermint , prune, senna leaf , tamarind, turkey rhubarb root, and uva ursi .

Herbs supposed to "strengthen" the body in general are found in many diet formulas, including ashwagandha , cordyceps , Eleutherococcus , fo-ti, ginseng , maitake , reishi , schisandra , and suma .

Other herbs and supplements sometimes recommended for weight loss for reasons that are unclear include buckthorn, cayenne , chickweed, coenzyme Q 10 , cranberry , fennel , flaxseed , ginger , ginkgo , gotu kola , grape seed extract , hawthorn , licorice , milk thistle , parsley , passionflower , plantain , white willow , yellow dock , yucca , and zinc .

Numerous dietary methods have been proposed for aiding weight loss. The Mediterranean diet, which is relatively high in fiber and monounsaturated fats (eg, olive oil) has attracted attention as an effective method for weight management. 240 For information on two of the most popular “alternative” diets for weight loss, see the articles on low-carbohydrate diets and low-glycemic index diets. On average, it appears that all dietary weight loss approaches are about equally helpful, provided one sticks to the rules. 198-200, 213,220-224,231,244 However, it is possible that a low-GI and the Mediterranean diet are more beneficial than a low-fat diet in people with type 2 diabetes and pre-diabetes. 220,240

One study found that reducing consumption of high sugar beverages has a minor effect, if any. 201

It has often been suggested that adoption of a vegetarian diet enhances weight loss, but this has not been proven. 233