The obese brain: neuroendocrine modulations in the reward system

Abstract

Obesity is a widely acknowledged problem, reaching even epidemic proportions. Despite awareness of the severe adverse consequences on health, food is excessively consumed. Why? Food intake is strongly influenced by the homeostatic balance, but this process can be overruled by hedonic systems that promote overconsumption. The reward system is thought to play a role in this hedonic regulation of food intake. This review will discuss neuroendocrine modulations found in reward pathways that may underlie obesity, with the focus on dopamine. Modulations in the corticomesolimbic system of obese individuals include reduced expression of dopamine 2 receptors, elevated dopamine levels, hyperactivity of sensory cortices, reduced prefrontal cortex activity and enhanced mu-opioid receptor binding. Many of these are associated with drug addiction as well. Yet these modulations are not well understood and may rather be consequences of an energy dense diet.