LOS ANGELES – Pharmaceutical giant Allergan Inc. stands to win big from the federal government’s decision to make Lap-Band weight-loss surgery available to more overweight Americans.

The Food and Drug Administration on Wednesday cleared the way for marketing the procedure to patients who are significantly less obese than those who qualify now — a decision that would make an estimated 26.4 million more Americans eligible to consider the Irvine, Calif., company’s device. The approval also means that, according to company officials, 45.6 million Americans meet the criteria for Lap-Band surgery. That’s more than one in seven.

But some in the medical community worry that it could encourage overweight people to abandon traditional diet and exercise for a surgery that carries some serious risks.

“I’m very concerned,” said Dr. Ted Khalili, former director of bariatric surgery at Cedars-Sinai hospital and founder of the Khalili Center for Bariatric Care in Beverly Hills, Calif. “You can’t … think that this will be an easy fix.”

The Lap-Band is an inflatable ring that is surgically implanted around the upper part of the stomach. Once the surgical wounds have healed, saline solution is injected into the ring to expand it, limiting the amount of food that can be consumed during a meal.

Allergan spokeswoman Cathy Taylor said Thursday that although the Lap-Band is now available to a broader base of patients, it “is not intended for everyone.” Instead, she said, it is designed for a particular subset of people “with a health condition, who have failed conservative weight-loss therapies like diet and exercise and pharmacotherapy.”

The approval allows Allergan to market the device to patients with a body mass index, or BMI, as low as 30 if they have at least one weight-related medical condition, such as diabetes or high blood pressure, the company said. For a 5-foot-9-inch patient, that translates to a weight of about 203 pounds.

Over the last two years, four Southern Californians have died soon after undergoing Lap-Band weight-loss surgery at two clinics connected to a marketing campaign touting the toll-free number 1-800-GET-THIN, according to lawsuits, family interviews and coroners’ reports.

Allergan does not pay for the ads, which were created by a marketing company that directs prospective patients to clinics that perform the procedure using Allergan’s device. Robert Silverman, the lawyer who represents 1-800-GET-THIN and the two clinics named in the suits, said the ads include warnings about the risks of Lap-Band surgery. He said the lawsuits were without merit.

Allergan’s chief executive, David E.I. Pyott, said this month that he didn’t support the ads.

Allergan said it requires all surgeons who want to order and perform a surgery with the Lap-Band to first complete a proctorship and training program; have advanced laparoscopic skill; and “have the staff and resources needed to comply with the long-term follow-up requirements.”

FDA spokeswoman Karen Riley said the agency can’t control how doctors use the procedure because it has no authority over the practice of medicine. But she pointed out that the FDA did not give Allergan all it asked for.