Why hope that? Having enough calories is essential to being able to do strenuous work. Taking hunger out of the equation is the point of having a food reserve.
Really depends on your timelines. Prep for short-term disaster scenarios on a 1-2 week timelines should be manageable for most, and really we should all be doing it. Prep for longer timelines is much harder.
They used to call it "the law of twos" - you can live two minutes without air, two days without water, and two weeks without food.
So yeah, water is the big concern. Two weeks without food is the low end, but electrolyte imbalances can kill you even if you still retain plenty of stored calories.