Those who made a New Year's resolution to lose weight may want to leave diet pills out of their regimine.

The Food and Drug Administration issued a warning last month for people to steer clear of some 30 different diet pill brands.

"Some of the products claim to be 'natural' or to contain only 'herbal' ingredients, but actually contain potentially harmful ingredients not listed on the product labels," the release said.
  Read the entire FDA warning here.

Studies have proven that diet pills don't always work and, oftentimes, make people feel worse rather than healthier.

Sweating, constipation and lightheadedness are just a few of the many side effects of diet pills-- most of which are FDA approved.

Diet pills from other countries that are not FDA approved are prominently sold online. They can cause heart attacks, strokes and even cancer.

Still, they're popular because they claim to promote easy weight loss.

"The websites are designed to lure you in and give you great results," pharmacist Michael Mohundro said. "I think we've established in these cases that looks are indeed too good to be true."

College student Mallory Pulliam recently bought foreign diet pills online. Now that she's been warned, she says she "probably won't take" the pills when they arrive.

Good old fashioned diet and exercise are what doctors say really work.

Start off with 30 minutes of cardiovascular exercise at least three times a week. Cardio causes heavy breathing. Examples include walking, jogging, swimming and cycling.

Also, eat less than 2,000 calories a day. People are more likely to keep the weight they lose off if it is lost slowly-- about two pounds a week.

Although popping a pill is easier, a low calorie diet and regular exercise is more likely to give the best results with the least amount of risk.