Patients taking anti-obesity drugs will only see "modest" weight loss and many will remain significantly obese or overweight, according to a study published on bmj.com.
The study, which looked at the long-term effectiveness of anti-obesity medications, found that three drugs recommended for long-term use - orlistat, sibutramine and rimonabant, reduced weight by less than 5kg (11 pounds). This equated to a loss of less than 5% of total body weight. Guidelines from the National Institute for Clinical Excellence recommend stopping the use of anti-obesity drugs if 5% of total body weight is not lost after three months.
While making changes to lifestyle and diet are recommended as the initial treatment for obesity, the use of anti-obesity drugs is common. It's estimated that in 2005 global sales of anti-obesity drugs reached $1.2billion. Current UK guidelines recommend using drug therapy in addition to making lifestyle changes if a patient has a body mass index of greater than 30.
The Canadian researchers reviewed the evidence from thirty placebo-controlled trials where adults took anti-obesity drugs for a year or longer. The mean weight of the volunteers in all of the trials was 100kg (15.7 stone). The mean body mass index levels were 35 – 36.
Professor Raj Padwal and colleagues found orlistat reduced weight by 2.9kg, sibutramine by 4.2kg and rimonabant by 4.7kg. They also found that patients taking the weight loss pills were significantly more likely to achieve 5 – 10% weight loss, compared to those who took the placebo.