Beta-hydroxy beta-methylbutyrate (HMB) (for improving body composition only)
Conjugated linoleic acid (CLA)
(-)-Hydroxycitric acid (HCA)
Blue-green algae (Spirulina)
Reliable and relatively consistent scientific data showing a substantial health benefit.
Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.
Dietary changes that may be helpful for weight loss and obesity
In a preliminary study, breast-feeding during infancy was associated with a reduced risk of developing obesity during early childhood (ages three to four years).15
In a preliminary study, overweight individuals who adhered to a very-low-carbohydrate diet (25 grams per day initially, increased to 50 grams per day after a certain weight-loss target was achieved), with no limit on total calorie intake, lost on average more than 10% of their body weight over a six-month period.16 . The participants also engaged in aerobic exercise at least three times a week, so it is not clear how much of the weight loss was due to the diet. Blood tests taken during the study suggested that the low-carbohydrate diet induced a condition called mild metabolic acidosis, indicating that long-term consumption of this diet may not be entirely safe. Individuals wishing to consume a very-low-carbohydrate diet for weight loss or for other reasons should be monitored by a doctor.
Calories in the diet come from fat, carbohydrate, protein, or alcohol. Weight-loss diets are typically designed to limit calories either by restricting certain foods that are thought to result in increased calorie intake, and/or by emphasizing foods that are believed to result in reduced calorie intake. Some currently popular diets restrict fat while emphasizing fiber and a balanced intake of healthful foods. Others restrict carbohydrates, either to extremely low amounts as in the Atkins diet, or to a lesser degree, emphasizing foods low in the glycemic index or high in protein. Discussions of the research on these diets follow; however, it should be remembered that no diet has been proven effective for long-term weight loss, and many people find it difficult to stay on most diets.17 18
Low-fat, low-calorie, high-fiber, balanced diets are recommended by many doctors for weight loss.19 According to controlled studies, when people are allowed to eat as much food as they desire on a low-fat diet, they tend to lose more weight than people eating a regular diet.20 However, low-fat diets have not been shown to be more effective than other weight-loss diets that restrict calories.21 Nonetheless, a low-fat, high-fiber, balanced diet has additional potential benefits, such as reducing the risk of chronic diseases including heart disease and cancer.22 23
Preliminary research indicates that people who successfully lost weight got less of their total calories from fat and more of them from protein foods. They also ate fewer snacks of low nutritional quality and got more of their calories from “hot meals of good quality.”24 Other preliminary studies find that dieters who maintain long-term weight loss report using fat restriction and eating a regular breakfast as key strategies in their success.25 26
Low-carbohydrate, high-protein diets
Low-carbohydrate, high-fat diets such as the Atkins diet are very popular among people trying to lose weight. In a preliminary study, overweight individuals who adhered to a very-low-carbohydrate diet (25 grams per day initially, increased to 50 grams per day after a certain weight loss target was achieved), with no limit on total calorie intake, lost on average more than 10% of their body weight over a six-month period.27 The participants also engaged in aerobic exercise at least three times a week, so it is not clear how much of the weight loss was due to the diet. An analysis of other preliminary studies of this type of diet concluded that its effectiveness is primarily due to reduced calorie intake.28 Recently, three controlled trials found people using low-carbohydrate, high-fat diets lost more weight in six months than those using diets low in fat and calories.29 30 31 However, 20 to 40% of these dieters did not stay on their diets, and were not counted in the results. In addition, one of these trials continued for an additional six months, at the end of which there was no longer a significant difference in weight loss between the two diet groups. A recent 12-week controlled trial found that overweight adolescents also lost more weight with a low-carbohydrate diet than with a low-fat diet, even though they consumed 50% more calories than did the children on the low-fat diet.32 That study suggests that the weight loss occurring on the Atkins diet is not due entirely to calorie restriction. Blood tests suggest that low-carbohydrate diets induce a condition called mild metabolic acidosis, which might increase the risk of osteoporosis and kidney stones.
The effect of low-carbohydrate diets on cardiovascular risk is also an unresolved issue. The short-term studies discussed above found that blood cholesterol levels did not worsen with these diets. Other heart-disease risk factors (triglyceride levels and insulin sensitivity) actually improved with a low-carbohydrate diet. Some studies, however, have shown a worsening of certain cardiovascular risk factors in people using a low-carbohydrate, high-fat diet for up to one year. Adverse changes included increases in blood levels of homocysteine, lipoprotein(a), and fibrinogen,33 and a decrease in blood flow to the heart.34 Individuals wishing to consume a very-low-carbohydrate diet for weight loss or for other reasons should be monitored by a doctor.
Some research has investigated weight-loss diets that are high in protein, but moderate in fat and not as low in carbohydrate content as the diets discussed above. While this type of diet does not usually lead to greater weight loss than other diets when calorie intakes are kept equal,35 one controlled trial found greater body fat loss in women eating a diet almost equal in calories and fat but approximately twice as high in protein and lower in carbohydrate compared with a control group’s diet.36 Another controlled trial compared two diets similar in fat content but different in protein and carbohydrate content. People allowed to eat freely from the higher protein diet (25% of calories from protein, 45% calories from carbohydrate) consumed fewer calories and lost more weight compared with people eating the lower protein diet (12% of calories from protein, 59% calories from carbohydrate).37
Low glycemic index foods
Diets that emphasize choosing foods with a low glycemic index have been show to help control appetite in some,38 39 40 though not all,41 controlled studies. A controlled study in two phases found no difference in weight loss between a low and a high glycemic index diet in the first 12-week phase, but when the diets were switched for a second 12-week phase, the low glycemic index diet was significantly more effective for weight loss.42 A preliminary study reported that obese children using a low glycemic index diet lost more weight compared with a similar group using a low-fat diet.43
Adequate amounts of dietary fiber are believed to be important for people wishing to lose weight. Fiber adds bulk to the diet and tends to produce a sense of fullness, helping people consume fewer calories.44 While research on the effect of fiber intake on weight loss has not produced consistent results,45 a recent review of weight-loss trials that did not restrict calories concluded that higher fiber diets improved weight-loss results, especially in people who were overweight.46
Stabilizing food sensitivities
Although the relationship between food sensitivities and body weight remains uncertain, according to one researcher, chronic food allergy may lead to overeating and obesity.47
People who go on and off diets frequently complain that it takes fewer calories to produce weight gain with each weight fluctuation. Evidence now clearly demonstrates that the body gets "stingier" in its use of calories after each diet.48 This means it becomes easier to gain weight and harder to lose it the next time. Dietary changes need to be long term.
Lifestyle changes that may be helpful for weight loss and obesity
Many doctors give overweight patients a pill, a pep talk, and a pamphlet about diet and exercise, but that combination leads only to minor weight loss.49 When overweight people attend group sessions aimed at changing eating and exercise patterns, keep daily records of food intake and exercise, and eat a specific low-calorie diet the outcome is much more successful. Group sessions where participants are given information and help on how to make lifestyle changes appear to improve the chances of losing weight and keeping it off. Such changes may include shopping from a list, storing foods out of sight, keeping portion sizes under control, and avoiding fast-food restaurants.
According to most short-term studies, the effect of exercise alone (without dietary restriction) on weight loss is small,50 51 partly because muscle mass often increases even while fat tissue is reduced,52 and perhaps because some exercising people will experience increased appetites. The long-term effect of regular exercise on weight loss is much better, and exercise appears to help people maintain weight loss.53 54 People who have successfully maintained weight loss for over two years report continuing high levels of physical activity.55 Combining exercise with healthier eating habits results in the best short- and long-term effects on weight loss,56 57 and should reduce the risk of many serious diseases.58 59 60
Avoid weight cycling
People who experience “weight cycling” (repetitive weight loss and gain) have a tendency toward binge eating (periods of compulsive overeating, but without the self-induced vomiting seen in bulimia), according to a review of numerous studies focusing on weight loss.61 The researchers also found an association between weight cycling and depression or poor body image. The most successful weight-loss programs (in which weight stays off, mood stays even, and no binge eating occurs) appear to use a combination of moderate caloric restriction, moderate exercise, and behavior modification, including examination and adjustment of eating habits.
Nutritional supplements that may be helpful for weight loss and obesity
5-hydroxytryptophan (5-HTP), the precursor to the chemical messenger (neurotransmitter) serotonin, has been shown in three short-term controlled trials to reduce appetite and to promote weight loss.62 63 64 In one of these trials (a 12-week double-blind trial), overweight women who took 600 to 900 mg of 5-HTP per day lost significantly more weight than did women who received a placebo.65 In adouble-blind trial with no dietary restrictions, obese people with type 2(non-insulin-dependent) diabetes who took 750 mg per dayof 5-HTP for two weeks significantly reduced their carbohydrate and fat intake. Average weight loss in two weeks was 4.6 pounds, compared with 0.2 pounds in the placebo group.66
Supplementation with 3 to 4 grams per day of a bulking agent called glucomannan, with or without a low-calorie diet, has promoted weight loss in overweight adults,67 68 69 while 2 to 3 grams per day was effective in a group of obese adolescents in another controlled trial.70
Multiple vitamin minerals
Diets that are low in total calories may not contain adequate amounts of various vitamins and minerals. For that reason, taking a multiple vitamin-mineral supplement is advocated by proponents of many types of weight-loss programs, and is essential when calorie intake will be less than 1,100 calories per day.71
Pyruvate, a compound that occurs naturally in the body, might aid weight-loss efforts.72 A controlled trial found that pyruvate supplements (22 to 44 grams per day) enhanced weight loss and resulted in a greater reduction of body fat in overweight adults consuming a low-fat diet.73 Three controlled trials combining 6 to 10 grams per day of pyruvate with an exercise program reported greater effects on weight loss and body fat than that seen with a placebo plus the exercise program.74 75 76 Animal studies suggest that pyruvate supplementation leads to weight loss by increasing theresting metabolic rate.77
(-)-Hydroxycitric acid (HCA), extracted from the rind of the Garcinia cambogia fruit grown in Southeast Asia, has a chemicalcomposition similar to that of citric acid (the primary acid in oranges and other citrus fruits). Preliminary studies in animals suggest that HCA may be a useful weight-loss aid.78 79 HCA has been demonstrated in the laboratory (but not yet in clinical trials with people) to reduce the conversion of carbohydrates into stored fat by inhibiting certain enzyme processes.80 81 Animal research indicates that HCA suppresses appetite and induces weight loss.82 83 84 85 However, a double-blind trial found that people who took 1,500 mg per day of HCA while eating a low-calorie diet for 12 weeks lost no more weight than those taking a placebo.86 A double-blind trial of Garcinia cambogia (2.4 grams of dry extract, containing 50% hydroxycitric acid) found that the extract did not increase energy expenditure; it was therefore concluded that this extract showed little potential for the treatment of obesity at this amount.87 Nonetheless, another double-blind trial found that using the same amount of Garciniacambogia extract significantly improved the results of a weight-loss diet, even though the amount of food intake was not affected.88
The ability of 7-KETO (3-acetyl-7-oxo-dehydroepiandrosterone), a substance related to DHEA, to promote weight loss in overweight people has been investigated in one double-blind trial.89 Participants in the trial were advised to exercise three times per week for 45 minutes and to eat an 1,800-calorie-per-day diet. Each person was given either a placebo or 100 mg of 7-KETO twice daily. After eight weeks, those receiving 7-KETO had lost more weight and lowered their percentage of body fat further compared to those taking a placebo. These results may have been due to increases in levels of a thyroid hormone (T3) that plays a major role in determining a person’s metabolic rate, although the levels of T3 did not exceed the normal range.
The mineral chromium plays an essential role in the metabolism of carbohydrates and fats and in the action of insulin. Chromium, usually in a form called chromium picolinate, has been studied for its potential role in altering body composition. Chromium has primarily been studied in body builders, with conflicting results.90 In people trying to lose weight, a double-blind study found that 600 mcg per day of niacin-bound chromium helped some participants lose more fat and less muscle.91 However, three other double-blind trials have found no effect of chromium picolinate on weight loss,92 93 94 though in one of these trials lean body mass that was lost during a weight-loss diet was restored by continuing to supplement chromium after the diet. A recent comprehensive review combining the results of ten published and unpublished double-blind studies concluded that chromium picolinate supplementation may have a small beneficial effect on weight loss.95
A double-blind trial found that exercising individuals taking 1,800 mg per day of conjugated linoleic acid (CLA) lost more body fat after 12 weeks than did a similar group taking a placebo.96 However, two other studies found that amounts of CLA from 0.7 to 3.0 grams per day did not affect body composition.97 98 Most double-blind trials have found that larger amounts of CLA, 3.4 to 4.2 grams per day, do reduce body fat;99 100 101 however, one double-blind study of experienced strength-training athletes reported no effect of 6 grams per day of CLA on body fat, muscle mass, or strength improvement.102
Fiber supplements are one way to add fiber to a weight-loss diet. Several trials have shown that supplementation with fiber from a variety of sources accelerated weight loss in people who were following a low-calorie diet.103 104 105 106 Other researchers found, however, that fiber supplements had no effect on body weight, even though it resulted in a reduction in food intake.107
Biochemical and animal research show that HMB has a role in protein synthesis and might, therefore, improve muscle growth and overall body composition when given as a supplement. However, double-blind human research suggests that HMB may only be effective when combined with an exercise program in people who are not already highly trained athletes. Double-blind trials found no effect of 3 to 6 grams per day of HMB on body weight, body fat, or overall body composition in weight-training football players or other trained athletes.108 109 110 111 112 However, one double-blind study found that 3 grams per day of HMB increased the amount of body fat lost by 70-year old adults who were participating in a strength-training program for the first time.113 A double-blind study of young men with no strength-training experience reported greater improvements in muscle mass (but not in percentage body fat) when HMB was used in the amount of 17 mg per pound of body weight per day.114 However, another group of men in the same study given twice as much HMB did not experience any changes in body composition.
Amylase inhibitors are also known as starch blockers because they contain substances that prevent dietary starches from being absorbed by the body. Starches are complex carbohydrates that cannot be absorbed unless they are first broken down by the digestive enzyme amylase and other, secondary, enzymes.115 116 When starch blockers were first developed years ago, they were found not to be potent enough to prevent the absorption of a significant amount of carbohydrate.117 118 119 120 Recently, highly concentrated starch blockers have been shown to be more effective,121 122 123 but no published human studies exist investigating their usefulness for weight loss.
Chitosan is a fiber-like substance extracted from the shells of crustaceans such as shrimp and crab. Animal studies suggested that chitosan supplementation reduces fat absorption, but controlled human trials have found no impairment of fat absorption from supplementation with 2,700 mg of chitosan per day for seven days or 5,250 mg per day for four days.124 125 A double-blind study in Poland found that people taking 1,500 mg of chitosan three times per day during a weight-loss program lost significantly more weight than did people taking a placebo with the same program.126 Other studies using smaller amounts of chitosan have reported no effects on weight loss.127 128 129
One double-blind trial found 100 mg per day of DHEA was effective for decreasing body fat in older men,130 and another double-blind trial found 1,600 mg per day decreased body fat and increased muscle mass in younger men,131 . However, DHEA has not been effective for improving body composition in women or in other studies of men.132 133 134 135 136 137 138 139
Guar gum, another type of fiber supplement, has not been effective in controlled studies for weight loss or weight maintenance.140 141 142
The amino acid L-carnitine is thought to be potentially helpful for weight loss because of its role in fat metabolism. In a preliminary study of overweight adolescents participating in a diet and exercise program, those who took 1,000mg of L-carnitine per day for three months lost significantly more weight than those who took a placebo.143 A weakness of this trial, however, was the fact that the average starting body weight differed considerably between the two groups. A double-blind trial found that adding 4,000 mg of L-carnitine per day to an exercise program did not result in weight loss in overweight women.144
Animal and human studies have suggested that when soy is used as a source of dietary protein, it may have several biological effects on the body that might help with weight loss.145 A preliminary study found that people trying to lose weight using a meal-replacement formula containing soy protein lost more weight than a group not using any formula.146 However, controlled studies comparing soy protein with other protein sources in weight-loss diets have not found any advantage of soy.147 148 149 When soy protein is used for other health benefits, typical daily intake is 20 grams per day or more.
Blue-green algae, or spirulina, is a rich source of protein, vitamins, minerals, and essential fatty acids. In one double-blind trial, overweight people who took 2.8 grams of spirulina three times per day for four weeks experienced only small and statistically nonsignificant weight loss.150 Thus, although spirulina has been promoted as a weight-loss aid, the scientific evidence supporting its use for this purpose is weak.
Whey protein may aid weight loss due to its effect on appetite. In a preliminary study, people were given 48 grams of either whey protein or milk protein (casein). Whey consumption resulted in more hunger satisfaction and reduced the amount of food eaten 90 minutes later compared with casein consumption.151 However, a double-blind study found that men taking 1.5 grams per 2.2 lbs body weight per day of whey protein for 12 weeks along with a low-calorie diet and a strength training exercise program lost the same amount of weight and body fat as did a control group that followed a similar program, but took a casein supplement instead of whey protein.152
Are there any side effects or interactions with weight loss and obesity?
Refer to the individual supplement for information about any side effects or interactions.
Herbs that may be helpful for weight loss and obesity
Research has suggested that incorporating cayenne pepper into the diet may help people lose weight. Controlled studies report that adding 6 to 10 grams of cayenne to a meal or 28 grams to an entire day’s diet reduces hunger after meals and reduces calories consumed during subsequent meals.153 154 Other controlled studies have reported that calorie burning by the body increases slightly when 10 grams of cayenne is added to a meal or 28 grams is added to an entire day’s diet 155 156 157 However, no studies have been done to see if regularly adding cayenne to the diet has any effect on weight loss.
The herb guaraná contains caffeine and the closely related alkaloids theobromine and theophylline; these compounds may curb appetite and increase weight loss. Caffeine’s effects are well known and include central nervous system stimulation, increased metabolic rate, and a mild diuretic effect.158 In a double-blind trial, 200 mg per day of caffeine was, however, no more effective than a placebo in promoting weight loss.159 Because of concerns about potential adverse effects, many doctors do not advocate using caffeine or caffeine-like substances to reduce weight.
The ability of yohimbine, a chemical found in yohimbe bark, to stimulate the nervous system, 160 161 and to promote the release of fat from fat cells,162 163 has led to claims that it might help weight loss by raising metabolic rate, reducing appetite, or increase fat burning. Although a preliminary trial found yohimbine ineffective for weight loss, a double-blind study found that women taking 5 mg of yohimbine four times per day along with a weight-loss diet lost significantly more weight than those taking a placebo with the same diet after three weeks.164 165 However, a similar study using 18 mg per day of yohimbine for eight weeks reported no benefit to weight loss compared with a placebo. A double-blind study of men who were not dieting reported no effect of up to 43 mg per day of yohimbine on weight or body composition after six months.166 All of these studies used pure yohimbine; no study has tested the effects of yohimbe herb on weight loss.
Green tea extract rich in polyphenols (epigallocatechin gallate, or EGCG) may support a weight-loss program by increasing energy expenditure or by inhibiting the digestion of fat in the intestine.167 168 Healthy young men who took two green tea capsules (containing a total of 50 mg of caffeine and 90 mg of EGCG) three times a day had a significantly greater energy expenditure and fat oxidation than those who took caffeine alone or placebo.169 In a preliminary study of moderately obese individuals, administration of a specific green tea extract (AR25) resulted in a 4.6% reduction in average body weight after 12 weeks.170 The amount of green tea extract used in this study supplied daily 270 mg of EGCG and 150 mg of caffeine. While caffeine is known to stimulate metabolism, it appears that other substances besides caffeine were responsible for at least part of the weight loss. Although the extract produced few side effects, one individual developed abnormal liver function tests during the study. Additional studies are needed to confirm the safety and effectiveness of green tea extracts for promoting weight loss.
Coupled with exercise in a double-blind trial, a combination of guggul, phosphate salts, hydroxycitrate, and tyrosine has been shown to improve mood with a slight tendency to improve weight loss in overweight adults.171 Daily recommendations for guggul are typically based on the amount of guggulsterones in the extract. A common intake of guggulsterones is 25 mg three times per day. Most guggul extracts contain 5 to 10% guggulsterones and can be taken daily for 12 to 24 weeks.
Although no clinical trials have been done, there are modern references to use of the herb coleus for weight loss.172 Coleus extracts standardized to 18% forskolin are available, and 50 to 100 mg can be taken two to three times per day. Fluid extract can be taken in the amount of 2 to 4 ml three times per day.
Although historically used to stimulate appetite, bitter orange is frequently found in modern weight-loss formulas because synephrine is similar to the compound ephedrine, which is known to promote weight loss. In one study of 23 overweight adults, participants taking a daily intake of bitter orange (975 mg) combined with caffeine (525 mg) and St. John’s wort (Hypericum perforatum, 900 mg) for six weeks lost significantly more body weight and fat than the control group.173 No adverse effects on heart rate or blood pressure were found. Bitter orange standardized to contain 4 to 6% synephrine had an anti-obesity effect in rats. However, the amount used to achieve this effect was accompanied by cardiovascular toxicity and mortality.174
Are there any side effects or interactions with weight loss and obesity?
Refer to the individual herb for information about any side effects or interactions.