Herb-derived stimulants include caffeine and ephedrine as well as the herbs guarana and ma huang. Two or three of these stimulants are usually 'stacked' together in one weight loss product, often along with aspirin or willow bark. They are supposed to increase energy while stimulating fat burning. Most experts agree they do work when combined with exercise. Their safety, however, is another matter.
"Ephedra [which comes from ma huang] is effective ... particularly when combined with aspirin and other ingredients," says Heymsfield. "But it raises blood pressure and can cause fatal heart attacks, [heart] arrhythmias, and strokes. ... The ads are very deceptive for ma huang regarding safety."
Klauer and colleagues studied the weight loss potential of ephedra last year. "People did lose more weight with it," she says, "but their elevations in blood pressure remained high even after they stopped the drug. ... So, I really don't recommend ephedra."
Despite a family history of heart disease, would-be triathlete Matthew Martin chose a combination of caffeine and ephedrine as his fat-burning program. He did notice his heart rate speed up after he popped a pill, but it didn't bother him. He found that taking the pills boosted his energy enough to make him want to work out more and reach his fitness goals sooner. One month after stopping the program, he remains in good shape, but he's also still in full-blown triathlon training.
Essential fatty acids include conjugated linoleic acid (CLA) and flax seed oil. They are sometimes used in combination with garlic to increase muscle mass and burn fat. They seem to be helpful in animals, and some new research is showing promise in humans.
Michael W. Pariza, PhD, director of the Food Research Institute at the University of Wisconsin in Madison, has studied CLA. "The clinical evidence is certainly emerging that it can be helpful, particularly in controlling fat and weight gain," he tells WebMD. "We also have pretty good evidence that it relieves a lot of the adverse effects [such as dizziness and stomach problems] that people have when they are dieting."