Yare yare...
Ostensibly, drinking water before eating is just to make you feel fuller so in consequence you eat less.
But it wont contribute to your overall feeling of hunger through the day.
Let say you drink a gallon of water before your meal, will you eat afterwards? Not likely. But after you flush that water out of your system you will feel even hungrier (Because the body made an effort to flush the water).
This is exactly the problem with all that is related to fat loss, we over complicate it. More focus on the basics and for a long period of time will suffice to reach any goal (well, almost).