Essentially, they explain how the brain "neuroadapts" to high levels of stimulation to where you are just getting normal amounts of pleasure but with all the negative side effects of the food or drugs (e.g. caffeine) and then you have to go through a painful withdrawal period. The book is mainly about healthy eating and also fasting, but the ideas are more broadly applicable.
Essentially, they explain how the brain "neuroadapts" to high levels of stimulation to where you are just getting normal amounts of pleasure but with all the negative side effects of the food or drugs (e.g. caffeine) and then you have to go through a painful withdrawal period. The book is mainly about healthy eating and also fasting, but the ideas are more broadly applicable.
See also: https://en.wikipedia.org/wiki/Supernormal_Stimuli http://www.paulgraham.com/addiction.html