Obesity has become a major public health burden worldwide due to the huge social and economic impact derived from its related comorbidities . Excessive body weight has been estimated to account for 16 % of the global burden disease  and according to World Health Organization estimates, over 600 million adults are obese worldwide Obesity is described as a multi-etiological disorder and several factors have been shown to be involved in its onset and development . Despite the important progression in the study of obesity, prevalence rates continue to increase, suggesting that additional elements must be involved in the pathogenesis of this disease. Moreover, even if weight loss programs are effective, keeping the weight off continues to be an almost insurmountable challenge . In this context, new theories are arising regarding food intake. Understanding obesity as a food addiction is a novel approach that has garnered considerable attention. Some studies have shown an association between mood and the overall dietary pattern including specific nutrients . Recent research also shows that palatable and high calorie food may have addictive potential. Subjects chronically eat some foods in amounts larger than needed for staying healthy, which shows a loss of control in food behaviour . Additionally, a 40 % prevalence of food addiction has been shown in obese individuals seeking bariatric surgery . All these traces indicate that there may be a potential relationship between behaviour and weight gain.
The dopaminergic system is involved in a large number of behaviors including reward processing and motivated behavior. Thus, all drugs of abuse increase the extracellular concentration of dopamine (DA) in the striatum and associated mesolimbic regions . Di Chiara’s group has extensively showed that addictive drugs (e.g. amphetamine and cocaine) increase extracellular DA in the nucleus accumbens (NAc), a primary site for reinforced behaviors . Likewise, microdialysis has shown that exposure to rewarding food stimulates dopaminergic transmission in the NAc .
Furthermore, neuroimaging studies show that our brain response is similar in the presence of food and drug abuse: increased cell activation in the NAc, the brain’s pleasure center [9–11]. Neuroimaging studies in humans have also shown similarities between obesity and addiction. For example, both obesity and addiction are associated with fewer D2 dopamine receptors in the brain [12, 13], suggesting that they are less sensitive to reward stimuli and more vulnerable to food or drug intake. Thus, for example, individuals with the largest body mass index (BMI) had the lowest D2 values .
Specifically, this reduction in striatal D2 density correlates with reduced metabolism in cerebral areas (prefrontal and orbitofrontal cortex) that exert inhibitory control over consumption . Thus, obese subjects show greater activation of reward and attention regions than normal weight subjects do in response to palatable food images versus control images [14, 15]. This observation suggests that a deficit in reward processing is an important risk factor for the impulsive and compulsive behaviors showed by obese individuals. Taken together, these data could explain why in obesity and drug addiction the consummatory behaviors persist despite negative social, health and financial consequences. All these neurobiological data suggest that obesity and drug addiction may share similar neuroadaptive responses in brain reward circuits or action mechanisms.
Food addiction as a new piece of the obesity framework
Lerma-Cabrera, J. M., Carvajal, F., & Lopez-Legarrea, P.
As indicated above, obesity has become a major public health problem worldwide. Therefore, finding efficient strategies to fight this disease represents a big challenge for the international scientific community. Studying the possible role of food addiction in humans as an influencing factor in excessive food intake is attracting attention. More so, considering the interesting results obtained with animals. It is known that some cases of excessive food intake do not respond to physiological needs but to a psychological behavioural component that needs to be identified. Finding this component would allow the inclusion of behavioural therapy among the cornerstones of obesity treatment, thus achieving a multidisciplinary approach in accordance to the multifactorial origin of the obesity. This more realistic grasp may allow applying effective treatments, leading not only to greater weight loses, but also to a better chance of keeping the lost weight off. YFAS and PEMS tools offer a rigorous way to evaluate whether an addictive process contributes to certain eating disorders, such as obesity and binge eating. However, further research is needed in order to evaluate the food addiction hypothesis and its relationship to eating disorders. It is necessary to study the effect of psychological, behavioral, cognitive and physiological factors in the food addiction construct. In any case, certain foods (fatty, sugary and salty) have shown to have an addictive potential, thus implying the possibility of preventing and treating obesity.
Obesity, food addiction, neuropeptides, palatable food, binge eating
Lerma-Cabrera, J. M., Carvajal, F., & Lopez-Legarrea, P. (2015). Food addiction as a new piece of the obesity framework. Nutrition Journal, 15(1). doi:10.1186/s12937-016-0124-6