Ermm..... This is so far beyond basic militarytraining. Did you mean 5kg? And no water? There are special forces units that wouldn't be able to do this.
Full kit loadout is like 20 kilos, maybe 25-30 if you are the LMG/Nlaw carrier in your unit.
>Fast for 3-4 days (just to see what it feels like)(speak to your doctor first)
>Thirst for 1-2 days (just to see what it feels like)(speak to your doctor first)
No water for 2 days is MUCH worse than no food for 4.