Why do we crave sugar?  The short answer is, because our brain relies on it (in the form of glucose) as a source of energy in order to function properly.  This is reflected in a new study just published in Frontiers in Systems Neuroscience (December, 2014).  The hypothalamus senses how much glucose is stored in places like the liver and pancreas, and secretes a substance called glucokinase when stores are getting low.  This causes us to want to eat carbohydrates as a quick source of fuel.  What happens when stored levels get low, or when there is an inadequate level for optimal brain function?  Besides glucokinase being secreted, cortisol levels will go up in order to divert glucose to the brain from other areas.  Higher levels of cortisol are associated with immune suppression, weight gain, hormonal imbalances, hypothyroidism and tissue wasting, among other negative effects.  Fatigue, mental fog, and anxiety are likely to increase as glucose stores get low.  So we want to avoid drops in blood sugar.  Keep in mind that when stress occurs the brain has an even higher need for glucose as a source of energy to meet the demands of the stress.  How do we prevent drops in glucose?  One way to do that is to avoid skipping meals and to simply get enough calories throughout the day.  Another way to do that is to consume enough non-starchy carbohydrate, such as most fruit, while minimizing starchy carbohydrate, such as grains.  It is sometimes possible that functional issues with the pancreas (insulin or glucagon secretion) or liver (glycogen storage) can be involved, so optimizing their function may be warranted.