Yes, I do know that waiting until thirst is felt means dehydration has already begun.
FWIW I quit drinking all sodas even diet soda, and drink only seltzer for thirst quenching. Seems to work.
What about drinking a glass of water before meals to limit food consumption? Real question.
You need to be careful with consuming carbonated water, because it is shown to inhibit mineral absorption.
Remember, many people who over induldge in food are over fed and under nourished. Many times the body creates cravings to get nourishment, so to use water as a tool to limit food consumption, may be a bit shortsighted if you are not getting enough nutrients and absorbing them in your daily intake.
Water is very important to keep the heart from becoming inflamed, keep tendons and ligaments pliable, improve the health of skin, keep muscles and tissue free of harmful metabolic by products and improve cellular respiration. While fruit is another source of water, it is high in sugar content and a high consumption of fruit has been shown to raise triglycerides. It is a good practice to drink 6-8 ounces of water in the A.M with a 1/4 tsp of real salt or pink salt, to help improve electrolyte profile and prevent dehydration.
Great move on the sodas. And yes, water before a meal is fine to reduce some appetite and get your system prepared for ingestion.
A great trick to limit food consumption during meals is to eat some fruit first...sugar in the fruit will raise glucose levels in the blood quicker, which should drive down hunger pangs.