There are two ways to use this glitch:
1: Eat/drink a food item from your inventory. (This also works when bandaging yourself, applying morphine/splint, and pretty much any other action). When it goes into the players hands, click the red X button to remove it from his hands. He will continue to eat and be nourished, but he will not use anything up, since his hands were empty. This also works with handcuffs. While handcuffing someone, press the same X button. The handcuffs will leave your hands and stay in your inventory, but the victim will still be handcuffed. (haven't done this bu a friend has)
2: Eat/drink a food item from your inventory (your backpack, lets say). Remove your backpack while your character is eating. The food will remain in the backpack, but the character will finish the eating cycle and be nourished.