This North American multi-center, double-blind, placebo-controlled study enrolled 3,040 overweight or obese patients -- approximately 80 percent of them women -- from 72 medical centers in the United States and Canada.

Patients were randomized to receive for one year either a low daily, fixed dose of 5 mg of rimonabant, a higher dose of 20 mg of rimonabant, or a placebo.

After the first year, patients on either dose of rimonabant were rerandomized to receive either the same dose of rimonabant or a placebo for a second year.

Throughout the study, calorie intakes were reduced by 600 calories per day.

The primary objective of the trial was to assess weight loss over one year, and then to determine the ability of rimonabant to prevent regaining weight during a second year of treatment.

Secondary objectives included an assessment of improvement in risk factors associated with abdominal obesity (dyslipidemia), and glucose metabolism and metabolic syndrome.

Patients on the higher dose of rimonabant were far more successful in losing weight and maintaining weight loss than patients on the lower dose or in the placebo control group.

Some 62.5 percent of patients treated for the full two years with the higher dose of rimonabant lost more than 5 percent of their body weight compared to 36.7 percent of those on the low dose of rimonabant and 33.2 percent of patients in the control group.

Moreover, 32.8 percent of patients treated for the full two years with the higher dose of rimonabant lost more than 10 percent of their body weight compared to 20 percent of patients on the low dose of rimonabant and 16.4 percent of patients in the control group.

The researchers also reported that patients treated for two years with the higher dose of rimonabant reduced their waist circumference by an average of 3.1 inches compared to 1.9 inches for those on the low dose of rimonabant and 1.5 inches for patients in the control group.

The researchers also reported that those treated with the higher dose of rimonabant increased their HDL cholesterol (good cholesterol) by 24.5 percent compared to 15.6 percent for those on the low dose of rimonabant and 13.8 percent for those in the control group.

At the same time, patients treated with the higher dose of rimonabant for two years lowered their triglycerides by 9.9 percent, compared to 5.6 percent for patients on the low dose of rimonabant and 1.6 percent for those in the control group.

For those patients with metabolic syndrome at the outset of the study, approximately one third of those taking the higher dose of rimonabant for the full study period no longer had this problem at the end of the two years.

Diabetic patients were not included in the study, but researchers reported that patients on the higher rimonabant dose significantly improved their insulin sensitivity compared to those on the lower dose of rimonabant and on the placebo.

"The effect of Acomplia on HDL-cholesterol, triglycerides, fasting insulin and insulin sensitivity appeared to be twice that which would be expected from the degree of weight-loss achieved," the researchers reported.

The researchers also reported that side-effect and safety results derived from the trial were also encouraging.

"Side effects were mainly minor and short-lived," the researchers reported. They said 12.8 percent of patients taking the higher dose of rimonabant dropped out of the trial during the first year as a result of adverse events, compared to 9.4 percent taking the lower rimonabant dose and 7.2 percent of those in the control group.

They reported that the drop-out rate for those who continued treatment for a second year was 6.0 percent for those taking the higher dose of rimonabant, compared to 8.3 percent for those taking the lower dose and 6.7 percent for those in the control group.

"No differences were noted in the three groups with regards to scores measured by the Hospital Anxiety Depression scale," the researchers reported. And they said that in this trial and in two preceding studies, rimonabant was also shown to produce no significant EKG or heart rate changes.

"The results from this study data are consistent with the findings from two previous large-scale studies on Acomplia -- RIO-Lipids and RIO-Europe -- communicated earlier this year and add to the ever-growing body of evidence supporting the drug's efficacy and tolerability profile," the researchers concluded.

Dr. Xavier Pi-Sunyer, Chief of the Division of Endocrinology at Saint Luke's - Roosevelt Hospital Cente in New York and lead researcher on the study, added:

"The two-year results of the RIO-North America trial confirm that rimonabant is an innovative and promising tool for the long-term management of weight and associated cardiovascular risk factors in abdominally obese patients.

"There was no evidence that this drug in two years had something we have to worry about in regard to safety," he added.