It's already sold over-the-counter in the USA and the UK, and now GlaxoSmithKline (GSK) are applying to have a weaker version, called Alli, available in pharmacies throughout Europe.
Business is already brisk, with annual sales reaching $155m (lb75m) in the 12 months since it was first sold by American pharmacies.
But - do the weight-loss drugs work? Early trials of orlistat suggested that a third of obese people could lose up to 10 per cent of their initial weight, an impressive result that has never been replicated.
A review of 30 trials into orlistat, and other weight-loss drugs such as sibutramine and rimonabant, found that orlistat is the poorest performer, achieving an average weight loss of just 2.9 kg in a year. Sibutramine fared slightly better with a weight loss of 4.2 kg and rimonabant with 4.7 kg.
Worse, the drugs can increase the risk of heart problems. Orlistat is most likely to cause gastro-intestinal problems - and especially faecal incontinence, which a GSK executive has delicately described as "the oops factor", while sibutramine increases blood pressure, and rimonabant raises the chances of psychiatric disorders, including depression and aggression. This affects 6 per cent of all patients.
The World Health Organization says that "eating less and exercising more must remain the cornerstones of managing obesity". And nowhere did they mention popping a pill.
(Source: British Medical Journal, 2007; 335: 1194-9).