ORLANDO, Fla. – A second study confirmed that an experimental diet pill can help people lose weight and keep it off for up to two years, setting the stage for its maker to seek approval to sell it in America.

The drug, rimonabant, which the French company Sanofi-Aventis hopes to sell under the brand name Acomplia, trimmed nearly 16 pounds on average from people taking the optimal dose for two years, compared with 5.5 pounds for those who took dummy pills, doctors reported yesterday at a cardiology conference.

“The majority of the weight that was lost at one year is still maintained after two years. There is only a slight increase over that second year,” said Dr. Luc Van Gaal of University Hospital at Antwerp, Belgium, who led the company-funded study involving 1,507 severely obese people in Europe.

About two-thirds of American adults are overweight or obese; in European countries, one-third to half are obese. Diet drugs sold now are only for short-term use or have unpleasant side effects that make it tough to stay on them.

Acomplia works in an entirely different way, by blocking a “pleasure center” in the brain, leading people to eat less and acting directly on fat cells to prevent weight gain. Company studies suggest it also might help people quit smoking.

In a North American study of 3,040 obese people reported last fall, those given the higher of two doses of the drug lost about 19 pounds and kept it off for up to two years, compared with only 5 pounds for those given fake pills.

In the new study, those on the higher dose regained some weight in the second year but fared far better than those on placebo. Waistlines in the drug group were 3.4 inches smaller after one year and 3 inches after two.

The proportion of people with metabolic syndrome – a collection of unhealthy conditions such as high blood sugar and blood pressure and low amounts of “good” cholesterol – went from 42% at the start of the study to 21% at two years for those on the higher dose of the drug.