Larger people have larger metabolic loads. Since we know that water is the key to fat metabolism, it follows that the overweight person needs more water. Water helps to maintain proper muscle tone by giving muscles their natural ability to contract and by preventing dehydration. Water helps rid the body of waste. Again, adequate water helps flush out the waste.
Water can help relieve constipation.
When the body gets too little water, it siphons what it needs from internal sources. The colon is one primary source. But, when a person drinks enough water, normal bowel function usually returns. Retained water shows up as excess weight. To get rid of excess water you must drink more water.