it has to do with survivor mainly, and in frookies it effects your PoV time, if you start the game with 100% you get full PoV time, each time you win PoV tho, you go down in time =P http://i56.tinypic.com/9gyob7.jpg (thats the chart to see the different times, if you start @ 100%)
and with survivor it decides your food and water % to start with, and then when you get voted out, your health goes lower, and you would wanna bring it back up b4 you join again (by joining fastings or duels, or getting donations)