You open a packet meaning to have just a few, and somehow it's empty before you've decided anything. Chocolate after a hard day. Biscuits that seem to appear alongside every cup of tea. It isn't greed, and it isn't a lack of discipline. Some foods are built, tested and packaged to make stopping the hard part, not starting. Here's what's actually happening in your brain when the bag opens, why the usual advice doesn't work, and what genuinely helps instead.