Rightly or wrongly, I have always found carbs to be my friends. I frequently consume my own bodyweight in pasta at about 9pm after work, and when making sandwiches, no fewer than four slices will do. So when I took a DNA test to learn what kind of diet best suited my genetic make-up, the results came as a blow. I'd expected to be told I should follow a Mediterranean regime because, well, shouldn't everyone? Instead I was advised to switch to a low carb plan. It was sufficiently sobering to make me pause, my sandwich halfway to my lips.