A friend was discussing this same issue the other day. It is somewhat weird since the day/night cycle is in real time, but having food and drink be realistic would be somewhat ridiculous. With the timers as they are now, eating and drinking are a game mechanic which enhances the feeling of survival as it causes us to horde food instead of ammo, risk death in dangerous locales because we need sustenance, and fight tooth and nail against each other over a can of beans. I think the timers are okay as they are, we are all just being thrown off by the realistic day/night cycle.