It wasn't me; it was my brain - Obesity-associated characteristics of brain circuits governing decision-making.

Over the past years, evidence has accumulated that obesity is intimately linked to the integrity of the fronto-striatal system of the human brain. However, the nature and causality of this relationship remains elusive. The fronto-striatal system is responsible for higher order cognitive functions such as learning, working memory, decision-making and cognitive control. Further, it determines the individual propensity to actively seek out rewards in the environment or to avoid possibly punishing situations. One of the major neurotransmitters of this system is dopamine. Recently, we suggested that markers of obesity are linked to markers of the dopaminergic system in an inverted u-shaped manner, with profound differences between individuals with moderate and severe obesity. Cross-sectional observations of dopamine-associated functions such as general reward sensitivity and anticipation support this hypothesis. Because of the fundamental role of the dopaminergic system in cognitive domains such as learning, prediction formation, cognitive control, and working memory, obesity-associated changes in this system affect cognition beyond food contexts. Taken together, the reviewed literature suggest either a dynamic relationship between the dopaminergic system and markers of obesity during the development of obesity, possibly based on processes of neuroplasticity, or different endophenotypes in individuals with overweight/moderate obesity and severe obesity.