It wasn't long ago that the cause of food cravings was believed to be rooted in emotional problems and in the overweight individual's practice of "looking for love in food".  So-called weight-loss gurus would write books and give lectures, telling overweight people how they needed to look for love elsewhere in life and stop believing that food could fill their emotional void.

Today science knows better.  What may be the biggest (and often insurmountable) challenge to overweight people who want to lose weight is the fierce craving of foods high in carbohydrates and fats, and there is a reason those cravings can be impossible to ignore.  It is now understood that food cravings occur as the result of the body's response to chronic stress, a response which differs from the response to acute stress.   Acute stress is when there is an immediate perceived threat.  Under acute stress the body responds with a stress response, but after the perceived threat has passed the body returns to normal.  Chronic stress, as the term implies, refers to living under stress over a long period of time.  Under chronic stress the body remains under a stress response, and since it essentially senses the need to be returned to a normal state it begins to crave foods that will (at least temporarily) reduce/end the high-stress response state.  This is a process that is rooted in evolution.  Its also one to which anyone who has ever felt better after eating a chocolate bar can attest.
 

Under chronic stress glucocorticoid levels remain elevated.  This leads to maintaining high levels of hormones (corticotrophin releasing factor, which then regulates adrenocorticotropin) which incite the stress response.  Essentially, the stress response keeps itself going.   Since the effects of this stress response are not positive effects nature has built into the system a way to reduce/eliminate those negative effects.  From an evolutionary standpoint, animals and people are designed to respond to stress by eating high-energy foods in order to be ready for anything.   From the standpoint of even the most evolved and overworked mother of a few children, not only has Nature built in the cravings that are difficult enough to ignore, but maternal instinct, too, will drive the mother to eat high-energy foods in order to keep going for her family.  Under long-term stress the adrenal gland can become fatigued and “run out of juices”.  Adrenal fatigue can be misdiagnosed as “depression”.  Symptoms include craving sugar.
 

Researchers at the University of California, San Francisco, who identified a biochemical feedback system in rates which could explain the cause of food cravings in humans, suspect that the signal to inhibit the stress system may come directly from the fat deposits.
 

The Catch-22 of the obesity problem is that while chronic stress, itself, results in negative effects on the health, the very eating that reduces those effects also leads to health problems.  In addition to normal stress and extraordinary stress, trying to lose weight can add yet more stress, but having that weight, in itself, is also stressful. 
 

In a world where so much emphasis is placed on educating people about health eating (under the presumption that most people need that education) understanding the very real challenge faced by many people with a weight problem may be the education that is most needed.