The world is getting very fat, very fast. The obesity epidemic has spread to the Third World and it is likely 1 billion people will be obese by 2030. So how did it explode in places that, not so long ago, counted malnutrition and even famine as major concerns? Well it's mostly about the aggressive marketing and low prices of Western fast food. As globalisation and a little more money open up Third World markets, the first to step in are the likes of McDonalds and Coke. In this global production, we travel to China where the consumption of sugar and oil has sent the national scales spinning; to Brazil where global food companies have fundamentally altered traditional diets; to India where it's predicted 100 million people will soon be suffering diabetes and on to Mexico, where the weight problem is so pressing, stomach reduction surgery is offered for free. The diagnosis is stark: "No country has managed the transition to get rid of hunger without it shifting to obesity" says anti-obesity crusader Barry Popkin. In a world where we are bombarded with messages to eat more hundreds of times a day, it's clear that obesity is a ticking time bomb.