A second study confirms 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 the United States.

The drug, rimonabant, which the French company Sanofi-Aventis (search) hopes to sell under the brand name Acomplia (search), 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 Tuesday 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 (search) of University Hospital in 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. 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 percent at the start of the study to 21 percent at two years for those on the higher dose of the drug.

Dr. Sidney C. Smith, a former American Heart Association president and cardiology chief at the University of North Carolina, said this was especially important, since 47 million Americans have metabolic syndrome.

However, the drug has side effects: 13.7 percent on the optimal dose reported nausea compared with 5.5 percent taking dummy pills, though researchers said it tended to be mild and short-lived. Rates of dizziness and diarrhea were almost twice as common on the drug.

About 19 percent on the higher dose dropped out of the study because a problem occurred, but so did 13 percent in the placebo group. Depression was the reason for discontinuing for 2.8 percent on the higher dose of the drug and 1.6 percent in the placebo group.

Dr. Julius Gaardin, a cardiologist at Wayne State University who had no ties to the study or the company, called it and similar ones on the drug "truly landmark studies in the field of obesity."

He said "the safety profile was quite good" and obesity is such a serious problem that there ought to be higher tolerability of side effects than for drugs for other conditions.

Company officials say they are on track to seek Food and Drug Administration approval within a few months.

Dr. Elizabeth Nabel, director of the National Heart, Lung and Blood Institute, said health officials would welcome an effective obesity drug if it proved safe.

"The important message is that we want men and women to focus on heart-healthy behaviors, modifications in lifestyles that promote health," she said.

Smith said the drug could give people "a wonderful jump start," but that for long-term success, "there have got to be some improved behavioral and diet changes going on beyond taking a pill."