Whether waiting for a bus, playing outside or walking the dog during the colder winter season, everyone is looking for ways to stay warm. Luckily, the process your body uses to break down foods serves as an internal heater.

But when the weather is cold, some defensive strategies are also necessary to prevent your body from losing its heat to the surrounding environment. As the temperature difference between your warm body and its frigid surroundings increases, heat is lost more quickly. It becomes more of a challenge to maintain normal body temperature.

And two people with the same exact body temperature in the same exact environment may have very different perceptions. One may feel frozen while the other is completely comfortable. But beyond the subjective experience of coldness, researchers do know that natural physiological responses to cold as well as behavioral adaptations like bundling up!  can help keep your body around 98.6 degrees Fahrenheit and make sure you feel warm.

What your body does

Your blood courses through your body carrying nutrients, oxygen and other biologically important substances. And this delivery system also brings heat produced in the muscles to the skin, where it's released.

When you enter a cold environment, your body redistributes blood to the torso, protecting and maintaining the warmth of the vital organs there. At the same time, your body constricts blood flow to the skin. Narrowing the roads to the skin means less heat can make the journey, and so less is lost to the environment. And minimizing how much blood goes to the skin which is in closest proximity to the cold means you can hold onto more of your internal heat longer.

Another defensive strategy the body uses to stay warm is cranking up muscle activity. This, in turn, increases your metabolism and creates more heat. Think of a brisk winter walk when the mercury has really plunged your teeth may chatter and your arms and legs may shake uncontrollably in shivers. This seemingly nonproductive use of the muscles is actually an effort to increase body temperature by breaking down more nutrients to stoke your internal furnace.

Differences in body size, body fatness and metabolic activity influence how different individuals experience cold. Smaller people with lower levels of body fat lose more heat to the environment than larger people with more body fat. A bigger individual may have increased muscle mass, which is a producer of heat, or elevated body fatness, which functions as an insulator to reduce heat loss. These differences are not easy to change.