What is neuropsychology?
Neuropsychology is the science that studies the relationship between our brains and behaviours, and whose objective is to set light on the correlation between brain structures and their function, what is called cognition. Neuropsychology is considered a neuroscience since it is based on the scientific method to empirically test the theoretical models provided by cognitive psychology. Human cognition brings together all the processes that allow us to interact with ourselves, with the environment around us and to learn from our experiences. The most common cognitive functions are the following: Attention, orientation, memory, executive functions, language, social cognition, and visual/perceptual abilities. Since mid-19th century to date, neuropsychology has undergone a tremendous transformation, ranging from the purest localizationism, with the phrenology of Gall and the studies of lesions, as the mostly known cases of Broca and Wernicke, to the most blatant functionality that currently rules. Thanks to the different neuroimaging techniques (Computerized Tomography, Magnetic Resonance Imaging and Positron Emission Tomography, Photon Emission Computed Tomography, between others), we can photograph the functions of the brain´s circuits and their underlying anatomical structure. Moreover, standardised neuropsychological tests, which exist since Luria´s studies in the early 20th century, allow clinicians to better describe observable human behaviors and establish cognitive impairment profiles for their patients to better guide a given diagnosis. At present, there is a growing knowledge that not only neurological diseases are associated with cognitive impairment, but that also metabolic, systemic, immunological, and psychiatric diseases may affect our neuropsychological functioning, including overweight and obesity.
Obesity and Cognition:
How does obesity affect at the different life stages?
From an evolutionary perspective, storage of energy in the form of body fat is essential to survive periods of famine and protect the integrity of the human being. Originally a beneficial aspect, extra energy availability has recently become the leading cause of non-communicable diseases. Especially in urban areas, obesity has nearly tripled due to the faster pace of modern life, unhealthy food availability and accessibility, reaching more than 13% of the world’s population, and has been converted in one of the most serious public health concerns.
Obesity is now recognized as an independent risk factor for adverse neurocognitive outcomes, and severely obese people appear to be at even greater risk. In children, obesity is becoming more and more visible. Poor self-esteem, feelings of anxiety and depression, group rejection by peers, stigmatization, or even bullying are well-known consequences of obesity among children. What is less known is its effect on brain development. For instance, in early ages (2-3 years old) obesity is associated with reduced acquisition of verbal, social and motor skills and with a worse performance in activities of daily living. At school age, children with obesity often present a lower Intelligence Quotient (IQ) compared with children with a normal weight. In adolescence, obesity has been associated with worse results in executive functioning, especially processes such as inhibition, flexibility and decision-making. In young adults, impairment appears to be present in working memory (function involved in the processing, handling and temporary storage of information, which are necessary steps for proper learning). Overweight and obesity in the middle-age, has been found to be associated with less cognitive flexibility, less ability to control the brain’s reward system, less visual-spatial capacity and verbal memory, linking a higher body weight to cognitive dysfunction. In advanced ages, obesity often exacerbates cognitive impairment and increases the risk of progression to dementia.
The good news is that the impact of obesity on our cognition appears to be reversible. Through weight loss interventions, such as healthy diet, moderate exercise or bariatric surgery, people living with obesity often improve their cognitive performance. Addressing weight loss becomes especially important as it probably confers some protection against subsequent cognitive impairment and may become the key to early interventions for cognitive impairment.
Obesity: Cause or consequence?
Whether obesity is a cause or consequence of morphological and functional changes in the brain is a matter for debate. In fact, some studies support the premise that cognitive dysfunction precedes obesity while others support that obesity can cause cognitive impairment through the processes of reward and dietary restriction, among others. Middle-aged adults with a higher body weight appear to show differences in brain volume in areas such as the amygdala and entorhinal and parahippocampal cortex, which are structures responsible for immediate recall of information and context mediation, the influence of the context on the interpretation of a fact. Suggesting that adults with obesity are more sensitive to the visual stimuli of food and less able to resist them, when considering feeding in a negative context. Different volumes in prefrontal cortex and subcortical areas would predispose to an increase in food intake due, presumably, to impaired cognitive flexibility, inhibition, and ability to control the reward system.
Conclusions
Neuropsychology may facilitate a better understanding of patients with obesity and their behaviors and enhance treatment outcomes.
Memory and executive functions are the most affected areas of cognitive functioning related to obesity, although high variability is present in neuroimaging studies. Further research should be done to clarify the underlying mechanisms.
Weight loss interventions, including healthy diet, exercise, or bariatric surgery have been shown to improve cognitive performance.
Whether obesity is a cause or consequence of morphological and functional brain changes needs to be clarified.
About the author
Julia Vázquez is a clinical and research neuropsychologist working as pre-doc at Vall d’Hebrón Research Institute (VHIR) in different research projects focused on psychological factors and cognition in metabolic disorders. She has expertise in the neuropsychological assessment and treatment of neurodegenerative disease, brain injury and epilepsy patients at Neurology Services at different Hospitals in the city of Barcelona. She had dedicated part of her clinical and research practice to the diagnosis and treatment of learning and language disorders in childhood neurorehabilitation centres. Also, she had collaborated as a teacher of the Neuropsychology master’s degree of the Universitat Autònoma de Barcelona and she is author of contents about Language pathology of the Master of Neuropsychology of the Universitat Oberta de Catalunya. www.linkedin.com/in/julia-vazquez-neuropsychologist