The drug works by blocking fat absorption in the body after a person eats, resulting in the extra fat being excreted from the body via bowel movements.

The drug, which is manufactured by GlaxoSmithKline, has been shown in studies to cause pre-cancerous lesions in the colons of mice. There have not been any long term studies done of the drug's effectiveness and therefore the group believes that the FDA should not have approved it for use.

"What we do know is that these lesions occur much more frequently in people who do get colon cancer," said Dr. Sidney M. Wolfe, director of
Public Citizen’s Health Research Group. "Why do we recommend that everyone get a colonscopy at the age of 50? Because you pick up on these polyps when you do one. And, even though not all of the polyps are pre-cancerous, no (doctor) does a colonscopy without removing every single polyp that is found. And you do this because you know if you don't, it greatly increases the chances of getting cancer."

The FDA, responding to the group earlier in the year stated that there was not enough evidence linking the Alli drug to an increased risk of colon cancer.

“We conclude that the available evidence concerning orlistat's safety does not support a causal relationship between orlistat and colorectal carcinoma, nor does any of this information meet the criteria for market withdrawal,” the FDA wrote in its decision."
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