BOSTON -- The ads promise to increase energy while controlling your appetite and reshaping your body. But experts warn the ingredients in Brazilian diet pills are not proven to deliver on those promises and they may be dangerous.

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"These diet pills from Brazil contain not only untested amphetamines, but also tranquilizers, anti-depressants, water pills and laxatives all combined in the same pill," said Dr. Pieter Cohen of the Cambridge Health Alliance.

Cohen started studying these pills after unsuspecting dieters came to see him. They had flunked drug tests for employment and didn't know why. Others suffered medical problems.

The common side effects are insomnia, anxiety and palpitations," Cohen said. "But there are much more serious ones. Amphetamines have lead to serious life-threatening heart and lung disease."

The federal government is well aware of the problem. In fact, two years ago the FDA warned people to stop using these pills, pills that are still readily available on the Internet.

In 2006 the FDA warned consumers not to use Emagrece Slim and Herbathin products because they may contain controlled substances found in prescription drugs that could lead to serious side effects or injury.

The FDA said it continues to work to prevent these products from being imported. Team 5 tried to contact the companies by phone and e-mail but were unable to reach anyone for comment.

Despite the national efforts, Cohen said locally an underground market allows dieters easy access to these pills.

"In our study we found that the pills were coming directly from Brazil," Cohen said. "So as long as the pills are commonly prescribed in Brazil, they're going to be available in the United States as well."