My mum used to do this as a way of budgeting for the food shopping and i have started doing it too.  i write a menu each week so i buy only what i need from the supermarket.  as i used to go on the way home from work, i'd be hungry and end up back home with biscuits, chocolate, crisps and other nonsense i didn't go in for!!  I've also started doing 2 weeks worth of food shopping and having it delivered - which is bliss.  The only thing i now go to the supermarket for on the way home is fresh veg.

I don't stick rigidly to the menu in that monday = egg and chips, tuesday = pasta, repeat to fade...... but i have 4-5 meals a week set.  I also plan out a couple of week sin advance when i know i'll be out for the evening to avoid having food in which then goes off and needs throwing away.

It's definitely working as i'm spending a lot less in the supermarket now.