You don't need to lose weight, Gita
But Never mind your coffee and alcohol...
The Toilet Roll will be the single unit of currency in any post apocolyptic society. 
Did anyone see the Book of Eli ? ... Where a little vial of shampoo was an absolute luxury beyond price to a woman with long hair...
s'funny.. when I was paranoid about 18 months ago and thinking about 'survival' I even watched a vid on youtube about how to skin a rabbit... I was thinking, well, you know... 'best get prepared'
Sheussh... wish I never watched it.
How would I know, that my diet would change voluntarily in the next 12 months... and now I find I can happily go without meat...so I wouldn't be forced to kill and skin Peter Rabbit after all.
See, some things, you just can't see...
Whatever happens... YOU will still exist. (until you don't). So logically, that's the best bit to work on, isn't it? Anything material can be taken away from you...
or given to you.
The other stuff is yours to keep.
K