I went back and re-read this section in the Golden/Tipton book. My initial post was not quite accurate on this point. Both carbohydrates and fats release water into the body when metabolized, it is protein that is the water hog when digested. I didn't want my post to mislead anyone.

Protein digestion yields urea which is toxic and it takes a fair amount of water to clear urea from the body. Carbs provide easy energy faster and are recommended by Golden/Tipton over fats & protein.

Metabolizing carbs & fats can yield 300-500mL of available water per day. Combined with a survival water ration of 500mL, this additional metabolic water can be a significant factor in surviving dehydration.