Neuroscience of food decisions in obesity and after bariatric surgery: the role of inflammation, insulin resistance and microbiota (original) (raw)

Obesity is a complex phenomenon whose pathophysiology encompasses the disruption of several feedback loops between the digestive tract, central nervous system, adipose tissue, immune system and intestinal microbiota. Peptides and neurotransmitters such as insulin, inflammatory cytokines, endogenous opioids and dopamine also come into play in the onset of dysfunctional eating behaviors and neuropsychological and emotional issues commonly observed in morbidly obese individuals. Low-level chronic systemic inflammatory processes, insulin resistance, and alterations of microorganisms in the intestinal flora secondary to obesity affect the brain, causing breakdowns in countless mental processes, including the regulation of emotion, motivation, impulsiveness, and even in cognitive processes such as attention, concentration and reasoning, thus compromising food decision-making. In addition, obese individuals often exhibit distortions of the pleasure related to eating when compared to lean individuals, i.e., they exhibit greater intensities of “liking” and “wanting” caloric foods. Functional neuroimaging studies show that, when exposed to sensory stimuli related to high-calorie foods, obese individuals show greater activity within brain structures related to reward processing (such as the mesencephalic tegmental ventral area, nucleus accumbens, amygdala, and the orbitofrontal cortex), as well as lower activity of the dorsolateral prefrontal cortex, which is associated with cognitive control. This anomalous pattern of brain activity is reversed by bariatric surgery, which would eventually impact pathophysiological processes of the brain, improving many behavioral symptoms of obesity. This manuscript aims to present a perspective on obesity and its surgical treatment based on neuroscience, emphasizing the pathological processes underlying the disruptions in eating decisions of the obese and how such disturbances are improved by bariatric surgery. Keywords: neuroscience, obesity, bariatric surgery, neuropsychology, reward.