1. You must have level 50.
2. Get a kitchen timer to ensure that you can leave the game sit for awhile, and not die (as your health constantly drops)
3. Get both magazines that help increase the effects of food
Preferably, you'll have the Mega Blaster unlocked (I can't remember what achievement gives you it, but it's very helpful to have it for the baddies).
Start off by getting both food magazines. I am unsure where they lie (I want to say in the easternmost and south-eastern most book stores), but obtain them ASAP while getting food items along the way.
Once you've obtained a few food items, as well as a gun or sword (a sword book helps too), find a good place to hide. Find out how long Frank can survive on the amount of food you have (usually 1 minute per bar...give or take), and set the timer for that amount minus one minute, to ensure you can feed in time.
Slowly use up your rations as need be. Save one food item, so when you go out 'hunting' again, you'll have extra just in case.
It's not hard, just time consuming. My profile should say I have the 5-day, but not 7-day achievement. I was mid way through day 6 when I died due to starvation - I set my clock for one minute too long.
Back from the dead, I'm afraid.
