Obesity and Brain Positron Emission Tomography

Obesity, an increasingly common problem in modern societies, results from energy intake chronically exceeding energy expenditure. This imbalance of energy can be triggered by the internal state of the caloric equation (homeostasis) and non-homeostatic factors, such as social, cultural, psychological, environmental factors or food itself. Nowadays, positron emission tomography (PET) radiopharmaceuticals have been examined to understand the cerebral control of food intake in humans. Using ¹⁵O–H₂ PET, changes in regional cerebral blood flow (rCBF) coupled to neuronal activity were reported in states of fasting, satiation after feeding, and sensory stimulation. In addition, rCBF in obese subjects showed a greater increase in insula, the primary gustatory cortex. ¹⁸F–fluorodeoxyglucose PET showed higher metabolic activity in postcentral gyrus of the parietal cortex and lower in prefrontal cortex and anterior cingulate cortex in obese subjects. In addition, dopamine receptor (DR) PET demonstrated lower DR availability in obese subjects, which might lead to overeating to compensate. Brain PET has been utilized to reveal the connectivity between obesity and brain. This could improve understanding of obesity and help develop a new treatment for obesity.