If you are overweight/obese and are taking an anti-obesity drug do not be surprised if your weight loss is only modest; neither should you be surprised if you continue being obese/overweight, according to an article in The British Medical Journal (BMJ), published today.

This study found that three commonly prescribed anti-obesity drugs – orlistat, sibutramine and rimonabant – resulted in weight losses of under 5% of total body weight – an average weight loss of less than 5kg (11 pounds). NICE (National Institute for Clinical Excellence, UK) recommends that if an anti-obesity drug does not achieve at least 5% loss of total body weight after three months it should be discontinued.

The authors explain that initial treatment for obesity should involve lifestyle and diet changes – even so, anti-obesity drugs are commonly used. Worldwide sales of anti-obesity drugs were approximately $1.2 billion in 2005. UK guidelines recommend the use of drugs for weight loss, as well as lifestyle and diet changes if the patient’s BMI (body mass index) is over 30.

The Canadian research team, led by Professor Raj Padwal, looked at evidence from thirty placebo-controlled trials where participants took anti-obesity drugs for at least 12 months. The participants’ mean weight was 100kg (15.7 stone, or 220 pounds), their mean BMIs were 35-36.

The researchers found that

— Orlistat reduced weight by 2.9kg (6.38 pounds)
— Sibutramine reduced weight by 4.2kg (9.24 pounds)
— Rimanabant reduced weight by 4.7kg (10.34 pounds)

The researchers also reported that those taking the anti-obesity pills were much more likely to lose 5%-10% of their body weight, compared to those on the placebo.

There were varying levels of health benefits, depending on which drug the participants took. Orlistat had an impact on reducing the incidence of diabetes, while one trial indicated that all three drugs lowered certain types of cholesterol levels. Adverse effects were recorded with all three drugs – rimonabant raised the risk of depression and/or anxiety. As none of the trials looked at death and disease rates linked to anti-obesity drugs, the researchers suggested that a study on this should be done.

The authors report that the drop-out rate in all these trials was high, about 30% to 40% of participants did not complete the trial. This indicates that the effectiveness of anti-obesity drugs are further undermined by poor adherence (compliance – patients not following instructions).

Accompanying Editorial

Professor Gareth Williams expressed concern at the idea of one day licensing anti-obesity drugs as OTCs (over the counter, drugs you can buy without needing a prescription) – something that already exists in the USA. GSK has applied for OTC status for Orlistat in Europe.

“Selling anti-obesity drugs over the counter will perpetuate the myth that obesity can be fixed simply by popping a pill and could further undermine the efforts to promote healthy living, which is the only long term escape from obesity,” Williams wrote.

“Long term pharmacotherapy for obesity and overweight: updated meta-analysis”
Diana Rucker, Raj Padwal, Stephanie K Li, Cintia Curioni, David C W Lau
BMJ, doi:10.1136/bmj.39385.413113.25 (published 15 November 2007)
Click here to view Abstract online

“Orlistat over the counter”
Gareth Williams
BMJ, doi:10.1136/bmj.39385.347049.80 (published 15 November 2007)
Click here to view First 150 Words online

Written by׃ Christian Nordqvist