Stankowska AUM, Gjedde A. Perspective food addiction, caloric restriction, and dopaminergic neurotransmission.People attempt to change their lifestyle when obesity impairs their quality of life. The attempts often fail when multiple habits must be changed in unison. Here we explore relations among food addiction, the neurobiology of habits, and caloric restriction, when people seek to return to normal eating behaviour, with particular emphasis on the role of dopaminergic neurotransmission. Severely obese individuals have specific neurobiological characteristics in common with drug abusers, including low availability of dopamine receptors in the striatum, impaired neuronal responses to dopamine, and reduced activity in prefrontal regions of the cerebral cortex. The neurobiological characteristics suggest that obese people also have a pathological dependence in common with addicts, in the form of food addiction. Malnutrition and dieting both relate to binge eating, possibly as a compensation for a reduced cognitive reward condition. The combination of caloric restriction and food addiction imparts a high risk of relapse as a result of further reduction of dopaminergic neurotransmission and the subsequent loss of reward. As with drugs of abuse, ingestion of large quantities of sugar in circumstances of uncontrolled eating increases dopamine release in the nucleus accumbens. This and other evidence suggests that abuse of food is a habit learned by means of mechanisms centred in the basal ganglia, with an increased risk of relapse in the presence of associative amplifiers. This risk is predicted by the relationship between dopamine receptor availability in the striatum and sensation-seeking in the form of an inverted U, suggested by recent findings, consistent with two opposite states of hypodopaminergic and hyperdopaminergic neuromodulation.
Summations> With neurobiological similarities among the brain functions of individuals with behaviour suggestive of addiction, obese individuals with reduced reward sensitivity suffer from pathological addiction to food. > Both undernutrition and dieting are positively correlated with strong craving for food and accompanying overeating, evidently as a compensation for reduced activity of neurobiological reward mechanisms. > The combination of caloric restriction and food addiction alone has a high risk of continued bouts of overeating as results of the reduced gain from dopaminergic neurotransmission maintained by repeated relapses. The risk can be diminished by lifestyle modifications that at the very least include exercise and counselling or group therapy. The inverted U-shaped model is a measure of the efficiency of a given individual's reward system.
Considerations> The neurobiological similarities among the brain functions of individuals with behaviour suggestive of addiction suggest but do not prove that obese individuals with reduced reward sensitivity in fact suffer from an addiction.