Altres ajuts: We would like to acknowledge Elena Delgado-Rico, Juan Verdejo-Roman and Jacqueline Schmidt Rio-Valle for invaluable help in collecting the data. We thank Jesus Pujol and Dídac Macià for kindly sharing part of the code used for data analysis. This study was funded by grants PI 0416/2008 (BRAINOBE) from the Andalusian Health Service (Consejería de Salud), and P-10-HUM-6635 (NEUROECOBE). Dr. Laura Moreno-López was funded by a Post-Doctoral Fellowship from the University of Granada.. Emmanuel A. Stamatakis is funded by a Stephen Erskine Fellowship, Queens' College, Cambridge, UK.

Obesity has been associated with brain alterations characterised by poorer interaction between a hypersensitive reward system and a comparatively weaker prefrontal-cognitive control system. These alterations may occur as early as in adolescence, but this notion remains unclear, as no studies so far have examined global functional connectivity in adolescents with excess weight. We investigated functional connectivity in a sample of 60 adolescents with excess weight and 55 normal weight controls. We first identified parts of the brain displaying between-group global connectivity differences and then characterised the extent of the differences in functional network integrity and their association with reward sensitivity. Adolescent obesity was linked to neuroadaptations in functional connectivity within brain hubs linked to interoception (insula), emotional memory (middle temporal gyrus) and cognitive control (dorsolateral prefrontal cortex) (pFWE < 0.05). The connectivity between the insula and the anterior cingulate cortex was reduced in comparison to controls, as was the connectivity between the middle temporal gyrus and the posterior cingulate cortex and cuneus/precuneus (pFWE < 0.05). Conversely, the middle temporal gyrus displayed increased connectivity with the orbitofrontal cortex (pFWE < 0.05). Critically, these networks were correlated with sensitivity to reward (p < 0.05). These findings suggest that adolescent obesity is linked to disrupted functional connectivity in brain networks relevant to maintaining balance between reward, emotional memories and cognitive control. Our findings may contribute to reconceptualization of obesity as a multi-layered brain disorder leading to compromised motivation and control, and provide a biological account to target prevention strategies for adolescent obesity