In fact, the FDA panel considering Xenical was at first split on whether to approve it, with nay-voters stuck on distressing medical points, such as the fact that the drug leaches vitamins from the body and disrupts the normal digestion process. Perhaps most alarming, one study the panel reviewed found that drug takers had a higher rate of breast cancer than those not on it. New data that the breast cancer cases didn't appear to be linked to the drug eased panel members' concerns enough for them to approve Xenical in May. But even after approval, Jules Hirsch, an internist and nutrition expert who served on the panel, says "there is a residual worry" over the breast cancer question.

And, since Xenical has been only tested for two years, its long-term effects add up to a big question mark. "We don't know what this drug does over long periods of time to gastrointestinal function," says Hirsch. "It's coating the intestine with a thin layer of fat. We just don't know what this will do to intestinal function over years."

Those interested in taking the drug seem less concerned with such medically weighty matters than with the drug's embarrassment-potential. As one dieter encountered in the weight-loss chat room at thriveonline.com delicately put it: "I heard it makes you mess your pants." The rumor was confirmed by another chatter, whose daughter is taking Xenical.

According to the Roche product information, such "adverse events" -- including anal seepage, oily spotting, orange stool and something disturbingly described as "fecal incontinence" -- occur in about a quarter of drug takers, but can be minimized by scaling back fat intake. That side effects increase according to the amount of fat a person consumes is helpful, at least when it comes to defending Xenical against charges of fueling an unhealthy compulsion to overeat. Like antabuse, a drug that makes alcoholics violently ill if they drink, Xenical could theoretically hem in behavior. But, even when eating light, the potential for oily spotting and emergency trips to the bathroom remain.

One might be willing to withstand such symptoms in the name of extending life or avoiding serious disease. Maybe. But would anyone risk such humiliation for the sake of obsessive vanity? Apparently so. Ben Krentzman, a weight loss specialist in Venice, Calif., reports that 18 of the 20 or so patients who have asked Krentzman about taking Xenical so far were not fat enough to meet the criteria. "People who want to lose five pounds can suffer the same torment as people trying to lose 500," Krentzman muses, by way of explaining the generalized lust for Xenical. (At 400 pounds, Krentzman says he is considering taking Xenical himself, but "wants to see how it all works out.") Krentzman will only prescribe the drug to patients who fit the official guidelines. But less scrupulous doctors can legally approve it "off-label" for just about anyone.

And those who can't get Xenical from a real doctor can get it from someone who plays one over the Internet. At least a dozen sites, most of which also sell Viagra, offer the diet drug "without a prescription," "in six easy steps," or "with complete privacy and confidentiality!" In lieu of a prescription, the buyer is usually asked to have an online consult, which involves answering questions about height and weight.

There is no way of verifying the information, of course, which means that the drug is available to pretty much anyone who has the roughly $120 it costs per month. (Insurance pays in only a minority of instances.) That worries some eating disorder specialists. "Bulimics quite consciously engage in the consumption of large amounts of calories followed by a behavior to avoid the consequences," says Tim Walsh, director of the eating disorders research unit at the New York Psychiatric Institute. As Walsh sees it, Xenical has the potential to be yet another consequence-avoiding tool, along with self-induced vomiting

No one makes any money off vomiting, however. So while marketing rights to the finger remain, for the moment, unclaimed, analysts project that Hoffman-La Roche will make some $3 billion from the drug. Roche, a pharmaceutical giant known for selling Valium, can't be held responsible for the abuse of its product, which it warns bulimics against using. (Bulimia, remember, is a medical condition, Xenical is a treatment.) But even while drug materials clearly state that Xenical is for the obese, the launch campaign seems to extend a extremely friendly hello to most everyone concerned about weight. The promotional information announces: "First and only in a new class for weight loss, weight maintenance, and reduced risk of regain."

And, to muddy matters more, Roche is promoting something called the "taste of healthy living campaign" in conjunction with Xenical. The PR extravaganza -- which extends to 18 cities and has employed everyone from high-end chefs to former New York mayor Ed Koch -- doesn't directly plug Xenical. But it does use the same shiny, blue folders and lettering as the Xenical materials to reach out to the population at large. That includes "Laura," a woman the promotional brochure describes as wanting "to maintain her weight of 128 pounds." "You'll see that you don't have to deprive yourself of foods you love to eat," assures the "healthy living" dieting guide, which, at the bottom of every page, says "Brought to you by Hoffman-La Roch Inc., maker of Xenical."

There is nothing wrong with the eat-light message of the campaign, in which high-end restaurants are paid to put "healthy living" icons near low-fat menu options. (So far, no chefs have accepted Roche's offer to directly promote the drug itself.) And there was nothing wrong with the "healthy-living" fare at Sonora, a New York Latin-fusion restaurant participating in the promotion. The lobster mango ceviche was tasty and the baked red snapper -- which comes in at a startlingly lean 117 calories -- were perfectly good. But what of the fact that the little healthy living icon on the menu will be associated with Xenical?

And, perhaps more to the point, what of the Dulce de Leche cheesecake listed on the menu just inches from the sensible fish dish? Surrounded by the constant celebration of richness, how could anyone not consider that Xenical would help them repel calories from cheesecake as well as from lighter fare? By reducing their calorie intake, wouldn't Xenical make people already partial to heavy foods more likely to indulge?

Desperation may dwarf such questions. Obesity contributes to some 300,000 deaths per year. It's hard to fault the ideal of making any dent in that number. And there's also the emotional relief to consider. Smith, the bank worker who participated in the clinical trials, for instance, says she was profoundly changed by her weight loss. "I enjoy life a lot more now," gushes Smith. "I feel so much better about myself."

Who wouldn't want that for our entire nation? Yet, given our ever-mounting desire for consequence-free excess, Xenical seems more likely to nudge us in the direction of even greater consumption, stretching our stomachs to accommodate bigger sundaes and whetting our appetites for the next big nutrient-blocking pharmaceutical. Something to think about as we pass a little oily wind and run like hell to the bathroom.