Is tracking your food purchases good for your health? - Published With a packet of biscuits in one hand and her smartphone in the other in the biscuits sucrées aisle of her local Hyper U supermarket west of Paris, Nathalie sees red. Literally. "Look at that!" she says showing me her phone. 0/100 is marked in red lettering. "This is one of Malo's [her 12-year-old son's] favourites but it's not only...