The number of people "dying" to be thin has doubled over the past three decades as the U.S. Department of Health and Human Services reports that at least 5 million people are now affected by anorexia. Now CBS 2 News has learned young women have found a new pill to feed their already dangerous weight loss addiction.

From thin to thinner to unreal -- the pressure to weigh less than everyone else has become an obsession again on the runway, on the red carpet, and in the school hallway.

Vicky Matropolo became obsessed with the scale weighing herself ten times a day. "It was a game," Matropolo said. "How far could I push the limit before someone noticed or intervened?"

Matropolo's weight eventually fell all the way to 88 pounds. She says she used over-the-counter diet pills and worked out two to three hours a day. Others are using what's being called the "size zero" pill, clenbuterol.

Clenbuterol is designed to treat emphysema in horses. It opens a horse's lungs to breathe, and in humans it opens fat cells to release fat, which is why the illegal drug is now the latest craze in celebrity diets.

"One side effect it give me is extreme shakes," says Matropolo. "My hands will just visibly be shaking and there's no control over it"

Trainer Jackie Warner sees clenbuterol gaining in popularity, but says in the end, users will be eventually gaining pounds.

"You will get fat -- fatter than you were before," Warner says. "There is not a magic pill, clenbuterol lasts three months and then you start gaining weight."

Warner says there are clear warning signs, weight loss being the obvious, but a denial of hunger, constant exercise, a sensitivity to cold temperatures, and greater amounts of facial and body hair. The extra hair growth is a result of the body's attempt to insulate itself because of a lack of fat.

Mastropolo never used clenbuterol because it wasn't the "in" pill during her addiction. Now, more and more young women are getting a hold of the drug in the black market.

Now in her 20's, Mastropolo is no longer anorexic. She says once she fed her body, she fed her mind and wanted to go to college.

"For six years I have not put myself on the scale because I refuse to live by a number," she said.