In November, 2007 the British Medical Journal published a new piece of meta-research into the relative effectiveness of Orlistat, Meridia and Acomplia. The difficulty with conventional research is that each individual study usually only involves a few hundred volunteers. Although these studies have to be "statistically significant", i.e. it must be reasonable to scale up the results so that they will offer a reasonable chance of being replicated in the community at large, one study cannot be anything more than an indicator. To get the best results, you need to take a number of published clinical trials and reanalyse the data to determine whether there are trends. This is what a meta-researcher does.

In this instance, the team analysed the data from thirty clinical trials representing 19,619 participants. To be included in the reanalysis, each trial had to last at least one year, the treatment with the medication had to be in conjunction with lifestyle changes to diet and encourage physical exercise, and follow the best practice methods of being randomised, double blind and placebo-controlled. Thus, the data covers a reasonable period of time (the longer the period of time, the more people are likely to drop out of trials — in this instance, an average of about 35% of the participants dropped out), and a more significant number of people.

The participants taking Acomplia had the highest range of weight loss at 4.1kg to 5.3kg. It also reduced the levels of high density lipoprotein cholesterol and triglycerides, improved blood pressure, and in patients with diabetes, gave better glycaemic control. But Acomplia was associated with a risk of anxiety, irritability and depression in about 6% of participants.

One of the factors that can affect the reliability of this meta-analysis process is that research journals may prefer to publish research with positive outcomes or only reports with positive outcomes are referred to journals for publication. This is called the funnel plot. Some pharmaceutical companies are accused of suppressing the publication of reports in which the outcomes are unfavourable to their products. In this instance, this did not appear to be a problem with the Acomplia findings. However, almost all thirty trials were funded by pharmaceutical companies. This may indicate the possibility of bias when the results prove positive. Secondly, the majority of the participants were relatively young and caucasian. This makes more general extrapolation of the results to other population groups more unreliable.

The National Institute for Health and Clinical Excellence (NICE) has recently changed its recommendation to accept Acomplia as being within National Health Service guidelines. The relevant rule for acceptance as an anti-obesity medication is that patients should consistently be able to lose at least 5% of their initial body weight after three months. That Acomplia has now satisfied this performance criterion is an endorsement of the medication’s effectiveness.

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