The first type of supplement, called metabolic optimizers, which include ephedra, caffeine and salicin (derived from willow bark), boost your metabolic rate, causing your body to burn calories faster. The second class, lipotropic substances, aid the body in fat mobilization, causing greater utilization of stored fat. These products include chromium, carnitine and hydroxycitric acid (HCA). Both classes of supplements have been around in various forms for quite a while but are now enjoying greater popularity among dieters.

Trying to cope with a weight problem is a dilemma expanding throughout modern society. According to a 1995 Harris poll, nearly 75% of Americans are overweight. Although it's well known that the way to lose weight is to expend more calories than you take in, supplements may be able to help you burn off extra calories.

Thermogenesis and You
Metabolic optimizers are supposed to aid weight loss through a process called thermogenesis. Thermogenesis is a natural process in which fat is burned to produce body heat. Fat that isn't burned is stored on the hips, thighs, stomach, etc. Thermogenic agents are designed to counteract your body's fat storage mechanisms by causing your body to maintain a higher metabolic rate-turning your internal thermostat up to burn fat faster. The thermogenic process can be jump-started by a number of factors including cold, exercise, certain dietary nutrients and metabolic optimizers.

Ephedra
The ephedra herb, also known as ma huang is one of nature's earliest medicines, known for over 5000 years to the Chinese, who used it to relieve allergies, coughing, wheezing and cold and flu symptoms. In the US, ephedra has been available since the 1800s.

The ingredients in ephedra include the alkaloids ephedrine, pseudoephedrine and norephedrine. Concentrated forms of these substances are used in today's over-the-counter cold, allergy and asthma relief formulas.

Ma huang's effectiveness as a weight loss aid is tied to its appetite suppressant and stimulant properties. By speeding up action of the thyroid gland, the ephedrine found in the herb acts a thermogenic agent, boosting the rate at which the body metabolizes fat and promoting weight loss. According to Mark Blumenthal, Executive Director of the American Botanical Council, "When used as part of a total package that includes diet modification and exercise, ma huang can be highly effective in the short run because it increases the speed of the body's metabolism and suppresses appetite."

Because of their strong stimulant effect, ephedra and its derivatives have engendered some controversy. However, in its long history, billions of doses of ephedra have been consumed without problem. But ephedra supplements should only be used as directed on product labels. People with cardiovascular problems, diabetes, thyroid or prostate dysfunction, high blood pressure and those taking MAO inhibitors, pregnant or nursing should avoid this herb.

Salicin Burns Fat
Salicin, a substance derived from willow bark-which is also the original source for aspirin, a related compound-can boost the burning of fat when combined with ephedra. An animal study in the American Journal of Clinical Nutrition found that while ephedra boosted calorie burning by almost 10%, when ephedra was combined with aspirin, extra calorie burning just about doubled. Another study in the Internatioanl Journal of Obesity showed that when overweight women took aspirin and ephedrine during a meal, their bodies burned off more calories than normal. (Eating a meal produces a thermogenic effect as your body expends energy in digestion. That's why dieters are told not to skip meals. Skipping meals lowers your metabolic rate, decreasing your calorie expenditure.)

Similar studies also show that caffeine, the stimulant that gives coffee its eye-opening kick, can also boost ephedra's thermogenic properties. But before using these combinations check with a health practitioner knowledgeable about nutrition. Aspirin or salicin may cause stomach upset in some people (although salicin is generally tolerated well.)

Carnitine: Lipotropic Amino Acid
To get carnitine into your system, you don't have to take it as a supplement. Your body already makes this vitamin-like substance. However, your body doesn't make that much. And it is said to be especially low in people with heart disease.

This non-essential amino acid (said to be non-essential because human bodies produce it) is a key ingredient in the formation of mitochondria membranes. Mitochondria are tiny structures in your cells that burn fats for energy. Consequently, sufficient carnitine is necessary for the movement of fat into the mitochondria where it is consumed. When not enough carnitine is present, the breakdown of long chain fatty acids slows down.

Said to improve the recovery rate for athletes (it may limit the production of lactic acid, a waste product in muscle tissue), carnitine can also lower cholesterol levels, boost levels of HDL (the good cholesterol) and decrease serum triglycerides (blood fats linked to heart disease). Not bad for a nutrient that coaxes fat into those teeny, ceullular, mitochondrial furnaces.

Go for the Chrome
Chromium-based supplements work as lipotropic agents by aiding insulin use in the body. This essential trace mineral is required for normal protein, fat, and carbohydrate metabolism. According to Dr. Michael Janson, author of The Vitamin Revolution in Healthcare and President of the American Preventive Medical Association (APMA), "Chromium is important for proper insulin activity. Insulin moves sugar into the muscle cells, where it is burned off as energy. Chromium improves the activity of insulin, and since insulin causes fat deposition, less of it means less fat deposition." Chromium has also been shown to build muscle tissue and to reduce LDL cholesterol, which has been linked to heart disease.

Although the body's minimum requirement is low, the American diet tends to be deficient in chromium, in part because the mineral can be difficult for the body to absorb. The fact that, in nature, chromium is most powerfully concentrated in brewer's yeast, wheat germ and liver-items most Americans rarely eat-probably hasn't helped either. Other natural sources of chromium include whole grains, molasses and beef. But it is estimated that 50% of Americans are chromium deficient. An early study found that overweight adults taking a chromium supplement lost an average of 22% body fat, while maintaining or gaining lean body mass. In another study, athletes consuming 200 mcg. of chromium a day showed an average loss of 7.5 lbs. of body fat after six weeks, without a corresponding loss of muscle tisue. Overall, although some studies question chromium's precise effects, many experts are optimistic about this substance because of its relationship to insulin in the body's metabolism.

Hydroxycitric Acid (HCA)
Another possible addition to the dieter's arsenal is HCA. In nature, HCA appears chiefly in a fruit called garcinia cambogia (sometimes also called Malabar tamarind or brindall berry), a citrus plant found primarily in Asia, where the rind is often used as a flavoring agent. HCA works by inhibiting the enzyme in the body responsible for converting carbohydrates into fat. HCA causes calories to be burned in an energy cycle similar to thermogenesis and acts as somewhat of an appetite suppressant. HCA is also said to have a role in reducing triglycerides and LDL cholesterol levels.

Several animal studies have shown that HCA caused significant weight loss without a reduction in lean body mass. In other words, the pounds that came off came out of fat stores, and not out of energy or muscle reserves. This means that HCA takes off not just weight but body fat, making it a potentially effective tool against weight regain.

Dr. Elson Haas, director of the Preventive Medical Center of Marin in San Rafael, CA, and author of Staying Healthy With Nutrition: The Complete Guide to Diet and Nutritional Medicine, believes that HCA can be a helpful aid for dieters when used in combination with eating habit changes and exercise. He recommends an HCA and chromium blend for optimum appetite suppression. "This combination can keep the appetite down and reduce sugar cravings," he says.

Although human research data on HCA is still in the preliminary stages, the animal study results are positive, and the supplement seems to have minimal side effects in most people.

Some Overall Recommendations
You are likely to lose weight faster if you eat sensibly. This means avoiding foods high in fat or sugar (which are the most likely to add to stored body fat), but it doesn't mean starving yourself. A sensible balanced diet, along with moderate exercise, is still the best prescription for weight loss. As Dr. Haas puts it, "I'm a firm believer in diet and exercise. Using supplements responsibly can help you to lose weight provided they're combined with dietary changes and exercise. They won't work if you don't change anything." No one is suggesting that dietary supplements are a miracle cure for being overweight-as always in self-health care, there are no magic wands. But, used as directed and combined with a good diet and exercise plan, you could find that these supplements might help you work your way to a slimmer you.