In pursuit of neural risk factors for weight gain in humans.

Obesity is a multifactorial disease associated with an increased risk of type 2 diabetes, coronary artery disease, cancer, and consequently, with a reduced length of life. Metabolic phenotypes of reduced energy expenditure have been associated with weight gain, but their contribution has been estimated to be relatively small. On the other hand, excessive food intake is likely to be the major determinant of positive energy balances and it is underlied by both non-conscious (homeostatic) and conscious (perceptual, emotional, and cognitive) phenomena processed in the brain. Functional neuroimaging is a promising tool to investigate these neural substrates in humans, because it provides a measurement of state-dependent brain regional activity, bridging the gap between neural events and behavioral responses. Using this technology, a few studies have provided the first evidence of functional differences between obese and lean individuals in the brain's response to energy intake and investigated the presence of neural risk factors of weight gain.