If you're still thinking about taking a diet pill, read the label for the active ingredients and check out whether there's any basis to their claims -- and whether they're potentially dangerous.

Find out the real deal on metabolism boosters, fat burners, carbohydrate blockers, fat blockers and more.

METABOLISM BOOSTERS
Ephedra
The FDA banned ephedra in December 2003 due to grave concerns about its safety. But while you won't find ephedra itself in diet-pill ingredient lists any longer, you will find ephedra-like compounds, including ephedrine, norephedrine, pseudoephedrine, methylephedrine and norpseudoephedrine, present in ma huang and other diet aids (often in combination with caffeine, which may exacerbate side effects). These compounds potentially present the same dangers as ephedra: elevated blood pressure, heart palpitations, insomnia, irritability, headaches, seizures, stroke, heart attack and even death. The safest route is to avoid all products that contain any of these substances.

Synephrine
After the FDA banned ephedra, diet-pill companies scrambled to find a possibly safer alternative. Enter synephrine, a substance made from the fruit of the citrus aurantium plant. Bitter orange, sour orange, green orange and zhi shi are other common names for this fruit. Synephrine acts almost the same way as ephedra does in the body, but with potentially fewer side effects like high blood pressure and increased heart rate. So far, clinical studies show that synephrine may in fact help reduce appetite and slightly increase metabolic rate, especially when combined with other stimulants such as caffeine or white willow. Obviously, anyone who has high blood pressure or other heart problems should not use any of these substances without prior approval from her doctor.