Foods with high water content include fruits and vegetables. Processed and packaged foods have much less water, and therefore usually more calories and fat as well. About 2.5 liters of water is necessary for metabolism for the average, sedentary individual. Consumption of 41 ounces of water daily would provide enough water for this purpose. Water is also formed with carbon dioxide when food is metabolized.
Water is lost through urine, skin, breath and the feces.
The use of protein as an energy source speeds up the body's hydration during exercise. The amount of water lost through sweat increases with exercise intensity. As water is lost, core temperature begins to increase. Weather plays an important role as well. More humid environments prevent the evaporation of water from the skin and cause an increase in core temperature.