Metabolic Water

Metabolic water is the water produced internally by your body as a byproduct of cellular metabolism, specifically the oxidation of macronutrients. When your cells burn carbohydrates, fats, and proteins for energy, water molecules are generated as a product of the chemical reactions. The oxidation of 100 grams of fat produces about 107 grams of water, 100 grams of carbohydrate yields about 55 grams, and 100 grams of protein produces approximately 41 grams of water. For an average adult consuming a standard diet, metabolic water production accounts for roughly 250 to 350 milliliters per day, representing about 8-10% of total daily water intake. While this may seem like a small amount, metabolic water is actually the primary water source for many desert-adapted animals. The kangaroo rat, for example, can survive its entire life without drinking water, relying solely on metabolic water from the seeds it eats. In humans, metabolic water production increases during exercise because of the higher rate of nutrient oxidation. People on high-fat ketogenic diets may produce slightly more metabolic water because fat oxidation yields more water per gram than carbohydrate or protein oxidation. However, this extra production is relatively small and should not be relied upon to meet hydration needs. Our water intake calculator factors in average metabolic water production when estimating your recommended daily intake, so the number you see already accounts for this internal water source. Pairing your calculator results with a balanced diet rich in fruits and vegetables maximizes both external and internal hydration.