Should you try a fad diet or a special supplement to help you reach your weight-loss goals faster? Get-slim-quick schemes can be tempting, but they're often ineffective, and they can sometimes even be dangerous.

Pills, teas and herbal supplements that promise to help you lose lots of weight quickly or melt fat in certain parts of your body don't work, according to the U.S. Food and Drug Administration. Plus, they can contain unsafe or untested ingredients that could have harmful side effects—like increased heart rate or blood pressure, stroke, seizure or even death.

Fad diets aren't much better. Plans that make you eat the same foods over and over again (grapefruit or cabbage soup, anyone?), avoid entire food groups or cut your calories very low might work for a little while, but you can't do them forever. Rapid weight loss can lead to health problems like gallstones.

If you're unsure whether a diet or weight-loss product is the real deal, try asking yourself one simple question: Does it sound too good to be true? If the answer is yes, then it probably is—and you should steer clear.

Let "slow and steady" be your motto. You should aim to lose one to two pounds per week by doing things you can stick with in the long run. That means eating right, keeping your portions in check and being more physically active.

And if you're not reaching your goal as fast as you hoped, talk with your doctor. He or she may be able to recommend healthy resources—like a dietitian or a proven weight-loss program—to get you on track.