Drugs more commonly used to treat depression and to help people stop smoking can also lead to significant weight loss among obese patients, according to the results of a study funded by drug maker GlaxoSmithKline and presented at the first annual Nutrition Week conference in the US this week.
A multi-centre, placebo-controlled study of the sustained-release formulation of bupropion hydrochloride - sold by GlaxoSmithKline under the brand names Wellbrutin SR and Zyban - showed that it could help stimulate significant weight loss in obese patients when combined with an energy restricted diet and exercise.
The study, lead by Professor James W. Anderson of the University of Kentucky College of Medicine, compared the changes in weight in patients receiving Bupropion SR at 300 mg/day and 400 mg/day to placebo during the first 24 weeks. Investigators then examined subsequent effects on body weight following an additional 24 weeks. In the subsequent 24 weeks, patients who initially received Bupropion SR continued with their treatment regimens, and subjects in the placebo group were randomised to active treatment of 300 mg/day or 400 mg/day of Bupropion SR.
More than 300 non-depressed, clinically obese men and women (as defined by a Body Mass Index of 30-44 kg/m2 or about 30 per cent - 100 per cent above their ideal body weight) participated in the investigation. Some 227 patients completed the initial 24 weeks and 192 completed the full 48 weeks.
All patients maintained a moderate exercise regimen in addition to a reduced-calorie diet (600 fewer calories per day than normally would be required to maintain the subject's current weight) facilitated by the use of a twice-daily meal replacement during the first 24 weeks, then once daily for the second 24 weeks. In addition, all subjects recorded food intake and physical activity in a daily diary and attended 12 visits to a clinic where lifestyle goals were reinforced.
During the initial 24-week period, individuals completing the study and receiving Bupropion SR lost significantly more weight than those in the placebo group. Individuals assigned to Bupropion SR 400mg/day lost a larger percentage of initial body weight (10.1 per cent) than those receiving Bupropion SR 300mg/day (7.2 per cent) or those receiving placebo (5 per cent).
Investigators then initiated a 24-week follow-on study to determine if weight loss could be maintained over a 48-week period. At the end of the second 24-week period, the average percentage weight lost from initial body weight for patients completing the study and receiving Bupropion SR 400mg/ day or 300mg/day was 8.6 per cent and 7.5 per cent respectively.
Completers who received placebo for the first 24 weeks and were switched to Bupropion SR 400mg/day or 300mg/day during the 24-week extension lost an average of 7.2 per cent and 6.4 per cent respectively of their initial body weight by week 48.
The most common adverse events experienced in this study at the highest dose that were greater than placebo were headache, dry mouth and diarrhoea. The researchers said that further study was necessary to determine conclusively the effect of Bupropion SR on weight loss in obese patients, particularly with respect to maintenance of weight loss, which in this study was not measured in a placebo-controlled setting for the full 48 weeks. The safety risks associated with the use of Bupropion SR for weight loss have also not been thoroughly evaluated.
"We are encouraged by these preliminary results in non-depressed obese patients," said Professor Anderson. "Even modest weight loss, if maintained, could produce significant health benefits."