Functional imaging in obese children responding to long-term sports therapy.

Functional imaging studies on responders and non-responders to therapeutic interventions in obese children are rare. We applied fMRI before and after a one-year sports therapy in 14 obese or overweight children aged 7-16 years. During scanning, participants observed a set of standardized pictures from food categories, sports, and pleasant and neutral images. We were interested in alterations of the cerebral activation to food images in association with changes in the BMI-standard deviation score (BMI-SDS) after therapy and therefore separated the observation group into two outcome subgroups. One with reduction of BMI-SDS >0.2 (responder group) and one without (non-responder group). Before therapy fMRI-activation between groups did not differ. After therapy we found the following results: in response to food images, obese children of the responder group showed increased activation in the left putamen when compared with the non-responder group. Pleasant images evoked increased insula activation in the responder group. Only the responder group showed enhanced activity within areas known to store trained motor patterns in response to sports images. Both the putamen and the insula are involved in the processing of emotional valence and were only active for the therapy responders during the observation of food or pleasant stimuli. Elevated activity in these regions might possibly be seen in the context of an increase of dopaminergic response to emotional positive stimuli during intervention. In addition, sport images activated motor representations only in those subjects who profited from the sports therapy. Overall, an altered response to rewarding and pleasant images and an increased recruitment of motor engrams during observations of sports pictures indicates a more normal cerebral processing in response to these stimuli after successful sports therapy in obese children.