10/24/2012 10:40 am ET Updated Dec 24, 2012

What Do You Crave?

Flickr: Malmaison Hotels & Brasseries

Cravings are, to me, some of the most interesting and most frustrating things when making lifestyle changes that involve food, alcohol or smoking, particularly because these habits often have a physiological origin. It is easy these days to get discouraged, but many times a craving has nothing to do with weakness or a lack of commitment -- it has a biochemical basis, which can be fascinating.

Since cravings are the result of physical processes going on in your body, distinguishing the source of the process can dramatically improve your success in making a lifestyle change. Now, here is where I think that the body's workings are simultaneously really cool and really creepy. Let's take the craving for carbohydrates. There are a number of reasons you may crave carbs, but let's look at the relationship between stress and this particular food group.

While our brains are very advanced and are able to produce complex thoughts, our bodies' response systems are still quite primitive. When the body is stressed in any way (upsetting thoughts, sleep deprivation, job loss, scary movies, car accidents -- just about anything in our busy lives), the adrenal glands go into action, and release cortisol.

Cortisol does many things, but let's focus on how it impacts cravings. When cortisol is released, it signals to the liver that you're going to need readily available glucose (sugar) in order to run from that angry lion. Truly, this is how primitive our nervous system is: We can't distinguish modern, non-life-threatening stressors. All stressors cause us to react the same way.

Your liver then begins to use its glucose reserves. If the stressor continues, it also sends you the message that you are going to need more glucose, quickly and in a readily available form. In modern society, that signal tells us to eat bread, cake, candy, pasta, cookies or potato chips because these are foods that most readily convert to glucose.

When you eat these foods -- and when they convert to glucose -- your blood sugar spikes, but then, quite quickly, it plummets, leaving you hypoglycemic. Hypoglycemia can cause you to feel tired, confused, anxious or shaky. Once you're in a hypoglycemic state, your body will crave more carbs in order to raise your blood sugar again. The cycle only continues from there.

You should note though, sometimes when you experience these cravings you're just plain hungry. The body is interpreting that as a need for carbs since it will provide energy you're lacking, although of poor quality. The solution to this issue is elegantly simple. Stay tuned.

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