Body heat is our internal energy. Our bodies generate heat constantly and regulate it to a normal temperature range (from 97 to 99 degrees Fahrenheit or 36.1 to 37.2 degrees Celsius).
Our bodies use water to stabilize body temperature. Water can absorb a lot of heat before its temperature rises, a trait that allows the water in every cell of our bodies to protect against sudden temperature changes. Maintaining our optimal body temperature is one more reason why it's so important to keep our bodies well-hydrated.
"To keep the body temperature in its proper range," says Joshua Thurman, M.D., "the body generates extra heat (for example, through shivering) if it needs to, and dissipates extra heat in sweat. This cooling process means, though, that to maintain body temperature water is often lost in sweat. The water lost must be replaced by drinking water, or you can become dehydrated."
Water and Muscle Mass
Burning calories through physical work or exercise generates heat from our muscles — and water comprises up to 75% of muscle mass. The water in the muscle cells exchanges heat with the water in our blood, which carries the heat away. In our brains, the hypothalamus senses the heat increase in the blood and activates the sweat glands.
Our sweaty skin serves as a heat exchanger. We cool down because the fastest-moving (hotter) water molecules escape as vapor, leaving behind the slower-moving (cooler) molecules. Air flow across the skin increases the effect. That's why a breeze helps to cool you off more quickly.
ABOUT OUR EXPERT
Dr. Joshua Thurman, MD is a board-certified nephrologist and Professor of Medicine specializing in renal medical diseases and hypertension at the University of Colorado School of Medicine. He received his medical degree from the University of Chicago Pritzker School of Medicine and his undergraduate degree from Harvard University. He has been in practice for more than 22 years.