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It is possible to survive without food for a while. You can fast, too. Which is also good for you :) (Depending on the way you do it of course, I wrote a short post about that before).

But I will be eating food from super-market (veggies, cheese) so that should not be very expensive so I'm sure I can cover that myself :).

Oh yeah, and I just noticed there's breakfast included in the hostel price :).
Though it's probably sort of food I don't eat, but in worst case I can eat that :).