Three scant years ago, Shanghai celebrated the 100th birthday of one of history’s most famous junk foods — the Oreo biscuit — with fireworks on the Bund and multi-storey neon adverts projected on to skyscrapers. But now China has put Oreo on a diet.

This is a country where, within living memory, millions starved to death. People will, to this day, tell you how they ate roots or shoots or even dirt to stay alive. Little wonder the Chinese market was a pushover for the ubiquitous black-and-white sandwich cookie.

Foreign treats were seen as healthier than local snacks, because they were imported from places that did not have such a vigorous tradition of poisoning residents with tainted ingredients, as was the fad in China. When I moved here in 2008, it took a while to get used to the notion that McDonald’s was a healthy option, purely because it was less likely to be toxic. Here, when mainlanders tell you something is “healthy”, they often mean that it won’t be immediately fatal.