Harvard psychologist Deirdre Barrett tackles the obesity and fitness crisis from an evolutionary standpoint. In the modern jungle of burgers, couches, and remote controls, obesity is an enormous and growing epidemic. Weight-loss books and diet gurus urge us to "listen to our bodies," but our instincts are designed for the African savannah, not food courts. The sugary and fatty foods that we, as hunter-gatherers, are programmed to forage used to be hard to come by. Radical changes are necessary and, fortunately, are biologically easier than small or gradual changes in diet. Barrett tells us how to reprogram our bodies, break food addictions, and ignore our attraction to artificial creations that appeal to our instincts more than the natural objects they mimic. Barrett delves into scientific research--from animal ethology to evolution--to show the disastrous direction in which our instincts have led us, and how, using our intellect, we can get back on course.