According to this week's New Scientist, women who recalled in detail a specific meal earlier in the day had less appetite 3 hours later than those who were asked to recall a different event.
Seems like reliving the detail of your lunch can lead to less snacking etc.. It only works with a meal you've had recently, not just random food. Apparently it does something to your hippocampus (something important in yer brain!)
Sounds like it's worth a try?