In a world where more people are overweight than underfed, according to the World Health Organisation, the fight against fat has become a $1.4 trillion (£726 billion) industry - and is set to increase to $2 trillion by 2012.

Pharmaceutical companies will cash in through new diet treatments and medical devices for an increasing number of gastric band operations. The market for food targeted at people trying to lose weight - and bigger clothes for those struggling to do so - will grow by more than 9 per cent annually until 2012, according to research by Credit Suisse.

As emerging economies become wealthier, their populations will grow fatter. The number of obese people in China is expected to rise by 347 per cent between now and 2015 as the Chinese buy more processed food.

Obesity not only reduces lifespan but can also cause illnesses such as type 2 diabetes and heart problems. In the United States alone, obesity costs $117 billion a year in healthcare.

As waistlines expand, the market for healthy foods is growing, too. The five food categories where sales grew the most around the world in 2006 - yoghurt-based drinks, fresh soup, fresh herbs and spices, fresh fish and seafood and ready-to-eat salads - are healthy. All of these had sales growth of between 10 per cent and 20 per cent in 2006, while the overall food market grew by 0.8 per cent. Drug companies specialising in anti-obesity products are set to benefit as governments try to deal with obese populations. In the United States last summer GlaxoSmithKline introduced over-the-counter sales of Alli, a lower-dose version of Roche's prescription-only Xenical. In trials, those who took it lost up to 50 per cent more weight than through dieting alone. Orexigen, a California company, is developing an anti-obesity product called Excalia. The drug, which tricks the brain into keeping the body's metabolism running fast, is still undergoing trials.

Analysts believe that the most effective - and lucrative - way to combat obesity is through surgery. Patients can lose between 50 per cent and 90 per cent of their excess weight, compared with 5 per cent to 10 per cent through drugs. Allergan, which makes the Lap-Band gastric band, expects sales to rise from $220 million to $850 million by 2012. The market for gyms and fitness equipment will also expand along with our waistlines.

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