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Joseph is not sure why Redux has not panned out for more of his patients. It may be that they put too much faith in the pill to make them thin without their having to eat less or exercise more. But Joseph also suspects a biochemical explanation. Redux, like "fen/phen" before it, boosts the levels of serotonin, a neurochemical that, among other things, signals the brain that the body has had enough food. "If a lack of serotonin is the reason patients are overeating, then Redux should work beautifully," Joseph says. "But if they are overeating for some other reason, then it probably won't do any good. The question no one has answered is, What percentage of overweight people have low serotonin levels?" Such studies are impossible, experts say, without doing a biopsy on living brain tissue.
Meanwhile, competition is heating up. Last month an FDA advisory panel recommended approval of a drug called orlistat that works on the gut instead of the brain--reducing caloric intake by blocking the body's ability to absorb fat. Orlistat has its problems--its side effects include intestinal leakage. That doesn't mean orlistat will not be a big seller, at least at first. But if folks buy it expecting weight-loss miracles, they are bound to be as disappointed next year as Redux users are today.
--Reported by Lawrence Mondi/New York and Dick Thompson/Washington