When I was on Physicians Weight Loss program I got this article in my packet and found it to be very true, I lost 40 pounds in 3 months and drank between 3-4 liters of water a day no exceptions thats 1+ gallons.

Water- How 8 glasses a day keep fat away

Incredible as it may seem, water is quite possibly the single most important catalyst in losing weight and keeping it off. Although most of us take it for granted, water may be the only true "magic potion" for permanent weight loss.

Water suppresses the appetite naturally and helps the body metabolize stored fat. Studies have shown that a decreas in water intake will cause fat deposits to increase, while an increase in water intake can actually reduce fat deposits. Here's why: The kidneys can't function properly without enough water. When they don't work to capacity, some of their load is dumped onto the liver.

One of the liver's primary functions is to metabolize stored fat into usable energy for the body. But, if the liver has to do some of the kidney's work it can't operate at full throttle. As a result, it metabolizes less fat, more fat remains stored in the body and weight loss stops.

Drinking enough water is the best treatment for fluid retention. When the body gets less water, it perceives this as a threat to survival and begins to hold on to every drop. Water is stored in extra-cellular spaces (outside the cells). This shows up as swollen feet, legs and hands. Diuretics offer a temporary solution at best. They force out stored water along with some essential nutrients. Again, the body perceives a threat and will replace the lost water at the first opportunity. Thus, the condition quickly returns. The best way to overcome the problem of water retention is to give your body what it needs-plenty of water. Only then will stored water be released. If yu have a constant problem with water retention, excess salt may be to blame. Your body will tolerate sodium only in a certain concentration. The more salt you eat, the more water your system retains to dilute it. But getting rid of unneeded salt is easy-just drink more water. As it's forced though the kidneys, it takes away excess sodium.

The overweight person needs more water than a thin one. Larger people have larger metabolic loads. Since we know that water is the key to fat metabolism, it follows that the overwight person needs more water.

Water helps maintain proper muscle tone by giving muscles their natural ability to contract and by preventing dehydration. It also helps to prevent the sagging skin that usually follows weight loss-shrinking cells are buoyed by water, which plumps the skin and leaves it clear, healthy and resilient.

Water helps rid the body of waste. During weight loss, the body has a lot more waste to get rid of-all that metabolized fat must be shed. Again, adequate water helps flush out the waste.

Water can help relieve constipation. When the body gets too little water it siphons what it need from internal sources. The colon is one primary source. Result? Constipation. But, when a person drinks enough water, normal bowel function usually returns.

How much water is enough? On average, a person should drink 8-8oz glasses every day. That's about 2 quarts. However, the overweight person need one additional glass for every 25 pounds of excess weight. The Amount you drink also should be increased if you exercise briskly or if the weather is hot and dry. Water should perferably be cold-it's absorbed into the system more quickly than warm water. And some evidence suggests that drinking cold water can actually help burn calories. When the body gets the water it needs to function optimally, it's fluids are perfectly balanced. When this happens you have reached the "breakthrough point." What does this mean?
Endocrine-gland function improves
Fluid retension is alleviated as stored water is lost.
More fat is used as fuel because the liver is free to metabolize stored fat.
Natural thirst returns.
There is a loss of hunger almost overnight.
Urge for constant urination decreases

If you stop drinking enough water, your body fluids will be thrown out of balance again, and you may experience fluid retention, unexlained weight gain and loss of thirst. To remedy th situation you'll have to go back and force another "breakthrough."