The Hypothalamus: Headquarters of the Set Point

About the size of an almond, your hypothalamus sits atop your pituitary gland at the base of the brain, just above the roof of your mouth. This well-protected location speaks to the vital importance of this brain region. In addition to controlling hunger and satiety, the hypothalamus keeps the body in balance, a process known as homeostasis (from the Greek homeo, meaning "like" or "similar," and stasis, meaning "standing still"). This internal balancing mechanism regulates your body temperature, as well as the amount of sugar, salt, water, and other substances in your bloodstream.

Most of the time, your temperature stays right around normal, or 98.6 degrees Fahrenheit, because the hypothalamus sends and receives a series of chemical messages that regulate your body temperature. It’s somewhat similar to the thermostat that controls your home’s heating system: When the temperature drops, the thermostat sends a signal to turn on the furnace. Likewise, if you’re cold, the hypothalamus checks in with other sensors in your body to see how it compares with the set point. If your temperature is lower than the set point, it sends a signal to your muscles, telling them to contract. That causes you to shiver, which helps you warm up. Conversely, if you’re too hot, you sweat, which helps you cool down. The body reactions happen involuntarily, without you even having to think about them. They’re perfect examples of your autonomic nervous system at work, which also plays a key role in homeostasis and your set point.

Source: George L. Blackburn, M.D., Ph.D., "Break Through Your Set Point: How to Finally Lose the Weight You Want and Keep It Off," 2008