Obesity is an epidemic in the West, but it is fast becoming a problem in other areas of the world as well, as people become more accustomed to eating unhealthy convenience foods and start to lead more sedentary lifestyles. Can weight loss supplements ease the problem and help a person shed those excess pounds? There may be evidence that they could do just this.

But wait! Let me say from the outset that no matter how many weight loss supplements you take, they won't do you any good at all if you continue to take in more calories that you burn. If you come across a supplement that claims that you will lose weight just by taking it -- even if you eat all the food you want and don't exercise -- stay away from it. Either it will have no effect at all, or it will make you very sick. Always remember that a healthy diet and good exercise are the essential components of an effective weight loss regimen. A weight loss supplement is just used to speed the process along just a little bit.

There are many kinds of weight loss food supplements out in the market today, and they have different functions and mechanisms. Some supplements function on the principle of thermogenics, that is, the body's process of making the metabolism run faster to burn fat faster and more efficiently. A number of herbal supplements can contain ingredients that stimulate the metabolism, such as ephedra (ma huang), green tea extract, caffeine, guarana, or synephrine. Synephrine encourages the breakdown of fat cells; guarana contains guaranine, whose effects are very similar to those of caffeine; and green tea not only promotes thermogenesis, it has numerous healthy effects on the body as well. Ephedra was a popular ingredient in many weight loss supplements, until it was banned because of associations with adverse events like heart attacks, stroke, and death.

Some diet pills and herbal supplements work to suppress the appetite and reduce food cravings. For instance, plantago psyllium -- derived from the seeds of Plantago ovato -- is said to cause a feeling of fullness, thereby discouraging more food intake. But perhaps the most famous appetite suppressant is hoodia, which is derived from a prickly plant that grows in South Africa's Kalahari Desert and which has been part of the diet of the bushmen there for centuries. Hoodia works by making the brain believe that the stomach is full. CBS correspondent Lesley Stahl even went to the Kalahari Desert to try hoodia herself, and she says that not only did she not feel hungry all day, but that she had no desire to eat or drink at all.

Some herbal supplements said to promote weight loss contain an ingredient called phaseolus vulgaris, which is extracted from the white kidney bean. These supplements are also known as carb blockers, or carbohydrate blockers. They prevent the body from absorbing starches, and are beneficial to those on a controlled-carbohydrate diet. Even more popular as weight loss supplements are so-called fat blockers, which, as the name implies, inhibit the body's absorption of fat. Chitosan, a substance derived from shellfish, is the main ingredient in fat blockers. It is an indigestible fiber that absorbs fat from foods. However, it is not suitable for people who are allergic to shellfish.

Other diet pills have the effect of increasing lean muscle mass or reducing fat, or both. Supplements that contain chromium picolinate are likely to be helpful and safe, according to human studies. Clinical trials also show that sometimes chromium has no effect on body weight, even though it can increase lean muscle and decrease weight. Still, there are concerns about its safe use in the long run. Another substance that shows similar promise is conjugated linoleic acid, which is found in beef and dairy foods. But again, more studies are needed to assess its effectiveness in weight loss and lean muscle mass-building. The same goes for hydroxymethylbutyrate (HMB), which is a by-product of the breakdown of leucine, an amino acid.

Sometimes it can be confusing to choose from among the many weight loss supplements available today, most of which have heavy marketing and advertising hype behind them. Whichever ones you choose, remember that they don't work magic; they should always be taken in conjunction with healthy eating habits and regular physical activity.