Our bodies evolved to keep us safe for as long as possible to ensure procreation and the safety of offspring.  That meant preparing our bodies to recognize physiological stress responses and react instantly and accordingly to keep us alive through danger.

One of the major dangers of human history has been famine.  With a constant possibilty of not having enough food to live, our bodies developed complex physiological strategies for holding on to energy resources when we were in "feast" times.  Essentially, in times of great prosperity we store fat and energy to get us through the hard times.


Of course, in modern Western society, there is virtually no risk of starvation.  We know this rationally, but our amygdala, or lizard brain, has developed over roughly 250 million years to react to purely pre-conscious stimuli.  The cycle of dieting and yo-yo weight loss so closely resembles feast and famine that we are basically training ourselves to hold on to extra weight.


Understanding aspects of human evolution can be critical in the consideration and treatment of obesity.  It can also help undercut weight discrimination by further proving the inadequacies of the calorie-in/calorie-out paradigm.