What renew says about seratonin levels - i hope that's true. It fits with my understanding but i haven't actually read any articles that talk about that. I haven't yet looked at the link posted and will too soon.
Anyway since as someone suffering from depression, i have noticed that low mood and greater appetite go together and i have also noticed that i can sometimes have a greater appetite around my periods so i really think there is something in this theory.
However, my advice for dealing with it would be to fill up on non-sweet foods. ADjust your calories upwards for the day but try to stick to a strict program of eating good food at fairly fixed hours - i mean meals and not constant snacking. If you prepare yourself in advance for this scenario, it might not be so hard to follow. You know its only for a few days and if you know what to do your resolve may be more effective.
Also have other strategies that you think will help avoid eating.
Be busy. Don't get bored.
Look after your mood before this time comes along so that you may suffer less with the pms.