Obesity has long been recognized as the major risk factor for many potentially life-threatening diseases such as diabetes, atherosclerosis, pulmonary embolism, hypertension, stroke, and cancer. Furthermore, it complicates a number of chronic disorders such as osteoporosis, osteoarthritis, gall bladder disease, respiratory diseases, and dyslipidemias. Many obese patients have been trying to lose weight or prevent weight gain. Although there are established ways such as a combination of dietary calorie restriction and maintaining regular physical activity, many of them are simply eating less fat to manage weight, few are using the recommended weight loss strategies. They expect to lose weight and improve body shape in short periods of time. In addition to reduced dietary intake, many obese people choose dietary supplements or diet pills as a method of achieving quick weight loss. Lifestyle behavior changes to lose weight can be difficult and time consuming; hence, dietary supplements are very appealing to this group of people. Among them, young adults, and women in particular, are interested in weight loss supplements. Dietary supplements for weight control or appetite suppressing generally include Garcinia cambogia, Ephedra sinica, chitosan, hydroxy-methylbutyrate, chromium picolinate, glucomannan, plantago psyllium, guar gum, pyruvate, hoodia gordonii, and yohimbe. Below are brief introductions for some common dietary supplements.

Ephedra sinica (ephedrine)

Ephedra sinica or Ma huang in Chinese is an evergreen shrub native to China and Mongolia. Ephedrine, a sympathomimetic agent referred to as ephedra alkaloid, is the primary active constituent of Ma huang. The main mode of ephedrine’s action is peripheral and causative. Ephedrine educes the noradrenaline (norepinephrine) release from presynaptic sites. It offsets the decrement in metabolic rate which normally occurs on caloric restriction. The decline in metabolic rate that accompanies caloric restriction, therefore, ephedrine is effective the initial weight loss stage by providing caloric restriction function. However, because of the evidenced safety concerns, the Food and Drug Administration (FDA) has recommended that people stop taking ephedrine-containing dietary supplements.

Hydroxycitric acid (HCA)

Hydroxycitric acid (HCA) is obtained from the Malabar tamarind tropical fruit (Garcinia cambogia) native to India. Hydroxycitric acid has been found to inhibit citrate cleavage enzyme, leading to reduced acetyl coenzyme A production and decreased fatty acid synthesis. Hydroxycitric acid has been shown to inhibit fat synthesis, reduce appetite, and lose body weight in the consumer. HCA reduces the conversion of carbohydrate calories into fats by inhibiting the actions of ATP-citrate lyase enzyme which converts citrate into cholesterol and fatty acids in the primary pathway of fat synthesis in the body. Hydroxycitric acid (HCA) does not stimulate the central nervous system and is therefore will not cause rapid heart rate, ervousness, hypotention, or insomnia associated with other dietary stimulants such as ephedrine, phenylpropanolamine or caffeine. The actions of hydroxycitric acid increase the glycogen production and storage while decreasing both appetite and weight gain. In addition, HCA also causes calories to be burned in an energy cycle in a way similar to thermogenesis.

Conjugated linoleic acid (CLA)

Conjugated linoleic acid (CLA) is a naturally occurring group of positional and geometric isomers of conjugated dienoic derivatives of linoleic acid. The major dietary sources of conjugated linoleic acid are beef and dairy products. CLA has beed reaserched for its potential application in weight loss profucts because of its antiatherogenic and anticarcinogenic properties as well as its function to decrease body fat while improving lean body mass. Conjugated linoleic acid reduces fat deposition in obese patient via increased fat oxidation and decreased triglyceride uptake in adipose tissue. Supplementation of CLA could improve lipid metabolism, insulin sensitivity, or body composition in obese patients with signs of the metabolic syndrome.

Chromium picolinate

Chromium is an essential trace mineral required for normal protein, fat and carbohydrate metabolism. Chromium is cofactor to insulin and enhances insulin activity by assisting insulin metabolize fat, convert protein into muscle and turn sugar into energy. Chromium potentiates the insulin action and thereby functions in regulating fat, protein and carbohydrate metabolism. Chromium plays a important role in energy production, appetite regulation, reduction of sugar cravings and improving lean body mass. Chromium picolinate is an organic compound of trivalent chromium and picolinic acid which a naturally occurring tryptophan derivative.

Green tea (EGCG)

Green tea has long been used to prevent and treat heart disease, high cholesterol, infections, acne, aging, dental caries, immune disorders, halitosis, periodontitis, dandruff, cancer, hypertension, rteriosclerosis, diabetes, high blood glucose, influenza hepatitis, and liver disease, etc. Green tea (Camellia sinensis) contains polyphenols e.g., (-)-epigallocatechin gallate (EGCG), a potent natural phytochemical antioxidant. One study showed EGCG to be active in inducing weight loss through decreasing the size of androgen sensitive organs. Epigallocatechin gallate increases metabolism, enhance the operation of insulin in the body, and lowers the respiratory quotient, which promotes the metabolic oxidation of body fat.

Chitosan

Chitosan is a cationic polysaccharide, which is produced from chitin, a amino polysaccharide (poly-N-acetyl glucosamine) derived from the exoskeleton of crustaceans (e.g., crustaceans such as crab, lobster, shrimp; insects; and molluscs). Unlike plant fiber such as bran and cellulose, chitosan is able to reduce the amount of lipid and cholesterol available for absorption and assimilation by the body. Chitosan is thus promoted as a supplement to assist in weight loss and thereby reduce the complications of obesity-associated conditions such as type II or non-insulin dependent diabetes and cardiovascular disease.

Pyruvate

Pyruvate, such as magnesium pyruvate or calcium pyruvate, is the mineral salt of pyruvic acid. Supplementation with pyruvate supplements is thought to improve exercise performance and enhance measures of body composition. Pyruvate has many pharmaceutical applications. It has been used in blocking fatty deposits in livers, retarding weight gain, diabetes teatment, extending sports endurance and inhibiting growth and spread of malignancy and retarding DNA breaks by blcoking generation of free radicals.

Yohimbe

Yohimbine, an indole alkaloid, is the main active constituent of the ground bark of Yohimbe (Pausinystalia yohimbe) which is a tall evergreen tree that is native to Central Africa. Yohimbine acts indirectly to induce the release and more efficient action of catecholamines already present in the central and peripheral nervous system. Yohimbine has been demonstrated to both increase circulating levels of norepinephrine which activates beta-adrenergic receptors on fat cells, and by directly occupying and blocking alpha-adrenergic receptors. These combined effects promotes a more efficient release of stored fatty acids and hence can promote quick weight loss during a weight loss program of reduced food intake and low intensity exercise.

Yerba mate

Yerba mate is an evergreen tree (Ilex paraguariensis) that is native to South America. Yerba mate contains xanthines, which are alkaloids in the same family as caffeine, theophylline, and theobromine, which are well-known stimulants also found in coffee and chocolate. The principal stimulant and diuretic effects of yerba mate have been attributed to the content of alkaloids. In addition to its stimulant effect due to its high methylxanthine content, yerba mate has also been used in the treatment of arthritis, constipation, slow digestion, hemorrhoids, hepatic disorders, fatigue, headache, rheumatism, nervous depression, improved cognition, hypertension and obesity.

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