According to research published this spring, people make healthier menu choices when calories are listed beside each item – but they make even better choices when they’re told how far they’d have to walk to burn off the calories consumed. This makes sense: for most of us, a calorie is a nebulous, hard-to-visualise thing, while a listing such as “burger: 2.6 miles” brings things sharply into focus. Somebody, it occurs to me, ought to design an app along these lines, for eating out: it would ask me what kind of food I’d like, then direct me only to those restaurants sufficiently far away that I’d neutralise the effect of the meal by walking there. In the mood for salad? There’s a place on the corner. Hungry for sausages, cheesy chips and a large slice of cake? Time to dig out the hiking boots.