It’s unusual to see a magazine editor pulling a box of McDonald’s French fries from her Chanel handbag at haute couture fashion week. But that was the unlikely occurrence in Paris last week – or so it seemed. The reality was decidedly calorie-free. Made of thick, spongey, bright red and yellow plastic, the season’s most prolific accessory among the style set is an iPhone case in the shape of a McDonald’s carton, by Italian fashion house Moschino. True to the spirit of fast food, counterfeit versions have appeared at lightning speed in markets and online. Obesity campaigners, however, have not been so quick to embrace the craze. Some members of the medical establishment question the wisdom of celebrating fast food at a time when one in four Britons is classed as obese and there are plans to lower the threshold for NHS weight-loss surgery for people with newly diagnosed type 2 diabetes to a BMI of 30, which could see an additional 800,000 people referred. Obesity expert and GP Dr Ian Campbell said: “My problem is that if kids are [using these iPhone cases] they are buying in to the whole fast-food concept. And while the occasional McDonald’s meal is…