Denne studen nevner 5 systemer som bidrar til at vi føler behov for karbohydrater. Den viktigste er at serotonin øker i hjernen, noe som over tid kan gi en avhengighet. De nevner også at evnen til å skille sult fra andre interne følelser kan bli dårligere, og at det gir behov for mat når andre ting i kropp og sinn er i ulage.
Serotonergic: Increased brain serotonin improves mood. Brain serotonin levels depend on the availability of its Trp precursor. Dietary carbohydrates increase the passage of Trp through the blood–brain barrier, unlike proteins, which alter LNAA. Faced with anxiety, an individual eats carbohydrates, which increase brain serotonin, thus improving mood.
Palatability and hedonic response: The pleasurable experience of eating food with high palatability immediately improves mood. This occurs in individuals with greater genetic sensitivity to sweet taste through the activation of the endogenous opioid system. Faced with anxiety, an individual eats a food with high palatability, activating the hedonic mechanism, which improvesmood.
Motivational system: Carbohydrates act in the motivational system in the same manner as abused substances. This increases dopamine and endogenous opioids, which are associated with a known pleasurable effect, improving mood. If this behavior is repeated over time, structural changes in the brain are produced that generate dependence on highly palatable foods.
Stress response: Faced with anxiety associated with stress, the HPA axis activates. Highly palatable foods activate the motivational system and reduce the HPA axis, thus regulating the stress system. Therefore, when faced with anxiety, highly palatable food produces a hedonic reward as well as reducing the state of anxiety.
Gene–environment: Eating is a coping tool to relieve negative emotions. The behavior is learned through inadequate parenting and environment. It also stems from an inability to distinguish hunger from other aversive internal states. There is greater susceptibility in carriers of the A1 allele of the DRD2 dopamine receptor and carriers of the short allele of the serotonin transporter gene.