The role of reward circuitry and food addiction in the obesity epidemic: An update.

The increasing worldwide prevalence of obesity is partially related to the ready availability of highly palatable foods which increases the incidence of hedonic, non-homeostatic feeding. The "food addiction" hypothesis postulates that exposure to these foods alters the brain's reward circuitry, driving an addiction-like behavioural phenotype of compulsive overeating. This review highlights recent evidence that examines changes in the mesolimbic dopaminergic circuit, the primary component of the reward system, associated with exposure to highly palatable foods and obesity. The majority of obesity studies in animals have not measured addictive-like behaviours, but reports of such behaviours have been restricted to experiments using models of binge eating. Where examined, the prevalence of addiction-like behaviour in overweight and obese subjects indicates that 10-25% of the population meets the Yale Food Addiction Score criteria. There is considerable overlap in the behaviours ascribed to food addiction and binge eating disorder, and food addiction scores correlate highly with measures of binge eating. We feel that more research is required in humans to determine whether food addiction is both behaviourally and neurobiologically distinct from binge eating disorder. While the reward circuitry is clearly affected by both highly palatable foods and diet-induced obesity in a similar manner to short and long exposure to drugs of abuse, the challenge for the future is to show that these neurobiological changes are associated with addiction-like behaviour.