By confessing its sins and introducing healthier snacks, the fast food industry is booming again

A few years ago it looked as though the odd crumbling monument in hick, southern towns would be all that remained of the fast-food industry. The obesity epidemic, class-action lawsuits and the stomach-churning revelations in Eric Schlosser’s book Fast Food Nation and Morgan Spurlock’s film Super Size Me had left sales at KFC, McDonald’s, Burger King, Wendy’s, Pizza Hut and Taco Bell in meltdown.

But in the past two years fast food has undergone one of the most remarkable turnrounds in business history. Forget the Fallen Arches. Fast food is on a tear.

Last week, the share prices of the two biggest chains hit record highs. McDonald’s stock is trading at $57, up from $26 in 2005. Shares in Yum Brands, which runs the largest number of fast-food restaurants in the world – 34,000 branches of KFC, Pizza Hut and Taco Bell – have risen fivefold.