WASHINGTON - Overweight Americans may be just months away from gaining a new ally in the battle of the bulge.

The fat-blocking pill, named Alli (pronounced "ally"), is meant to help the overweight and obese shed pounds as part of a diet and exercise program.

A panel of experts voted 11-3 late Monday to recommend that the Food and Drug Administration approve sales of the pill without a prescription. The drug is formally called orlistat and already is available for sale in prescription form as Xenical.

The FDA still needs to sign off on the recommendation, but it usually follows the advice of its outside panels of expert scientists and doctors.

If the FDA does OK the pill, it would become the first agency-sanctioned weight-loss drug available for purchase without a prescription.

Alli would have half the dosage of Xenical, but would be freely available for purchase by adults. GlaxoSmithKline Consumer Healthcare estimates 5 million to 6 million overweight Americans could buy the pills, which would cost $12 to $25 a week.

The prescription form, approved by the FDA in 1999, would continue to be sold by Roche.

"We are excited about the potential opportunity to provide consumers with an FDA-approved over-the-counter option that promotes gradual yet meaningful weight loss," said George Quesnelle, president of GlaxoSmithKline Consumer Healthcare North America.

In six-month clinical trials, obese people who took orlistat lost on average 5.3 pounds to 6.2 pounds more than did those who were given imitation pills. Once patients stopped taking the pills, they regained some of that lost weight, said Dr. Julie Golden, a medical officer in the FDA's division of metabolism and endocrinology products. Quesnelle said people could resume taking the pills or seek help from a doctor if they gain weight.

The panel requested the company conduct follow-up studies if the drug does reach the market, as well as rework the pill's label to ensure its proper use, panel chairman Dr. Alastair Wood said after the vote.

"I think the drug is safe enough to be OTC. . / . although there are some i's that need to be dotted and t's crossed," said Wood.

Orlistat acts by blocking the absorption of about one-quarter of any fat consumed in a meal. That fat -- the equivalent of about 150 to 200 calories -- is passed out of the body in stools, which can be loose or oily as a result. Other side effects include fecal incontinence, gas and oily spotting of undergarments. About half of patients in trials experienced such side effects, the company said.

Eating less fat helps control those side effects and cuts the intake of calories, the company said.

Glaxo said the drug helps the overweight slim down only when combined with a diet and exercise regimen. The drug's actual effect on weight loss is "gradual and modest," said Steve Burton, Glaxo's vice president of weight control.

"There is no magic pill for weight loss, and orlistat is not a magic pill. Orlistat is a tool that will help people control their calorie intake and modify their diet," said John Dent, the pharmaceutical company's senior vice president of research and development.

Many health experts remain divided over whether the drug should be made more readily available.

"I don't think it's a bad thing, the reason being there aren't that many side effects, and it's sort of a drug that may be helpful, especially for people who are eating a high-fat diet," said Judith S. Stern, a professor of nutrition and internal medicine at the University of California-Davis.

But the drug may not be as helpful as many dieters would like.

"I'm just concerned that people will perhaps take too much of this," said Joanne Ikeda, one of the founders of the Center for Weight and Height at the University of California-Berkeley. "My understanding is you can lose four or five pounds. I think most people want to lose more weight than that, and might not be satisfied" with taking the recommended dose.

Dr. Sidney Wolfe of the watchdog group Public Citizen urged the panel to reject the company's application. He called it a "desperate attempt to revive this barely effective drug by an OTC switch."

More than 22 million people worldwide have used orlistat in prescription form.