In the UK, the proportion of adults with obesity has been increasing significantly, with no signs of any reversal;1 this is despite the UK government ambitiously announcing in 2007 that England was to be the first country to reverse the trend in rising rates of obesity and the introduction of public health programmes such as Healthy Lives, Healthy People, and Change4Life.

One reason why obesity has proved difficult to control is due to the limited impact of pharmacological interventions. Adverse effects such as valve disease and pulmonary hypertension (as a result of fenfluramine and dexfenfluramine treatment), psychiatric disorders (associated with rimonabant) and increased risk of myocardial infarcts or stroke (due to sibutramine) forced withdrawal of drugs by regulators or resulted in voluntary withdrawal by manufacturers. Of those drugs for obesity that remain, many are short-term and only give modest results (<4 kg weight loss) while only one (orlistat) is licensed for long-term management; all are associated with common and unpleasant side-effects.2