Int J Obes (Lond). 2016 Feb 17. doi: 10.1038/ijo.2016.28.
Food craving is a driving force for overeating and obesity. However, the relationship between brain mechanisms involved in its regulation and weight status is still an open issue. Gaps in the studied body mass index (BMI) distribution and focusing on linear analyses might have contributed to this lack of knowledge. Here, we investigated brain mechanisms of craving regulation using functional magnetic resonance imaging (fMRI) in a balanced sample including normal weight, overweight and obese participants. We investigated associations between characteristics of obesity, eating behavior, and regulatory brain function focusing on non-linear relationships.
43 hungry female volunteers (BMI: 19.4-38.8 kg/m2, mean 27.5 +/- 5.3 s.d.) were presented with visual food stimuli individually pre-rated according to tastiness and healthiness. Participants were instructed to either admit to the upcoming craving or regulate it. We analyzed relationships between regulatory brain activity as well as functional connectivity and BMI or eating behavior (Three-Factor-Eating Questionnaire, scales: Cognitive Restraint, Disinhibition).
During regulation, BMI correlated with brain activity in left putamen, amygdala, and insula in an inverted U-shaped manner. Functional connectivity between putamen and dorsolateral prefrontal cortex (dlPFC) correlated positively with BMI, whereas that of amygdala with pallidum and lingual gyrus was non-linearly (U-shaped) associated with BMI. Disinhibition correlated negatively with the strength of functional connectivity between amygdala and dorsomedial prefrontal (dmPFC) cortex as well as caudate.
This study is the first to reveal quadratic relationships of food-related brain processes and BMI. Reported non-linear associations indicate inverse relationships between regulation-related motivational processing in the range of normal weight/overweight compared to the obese range. Connectivity analyses suggest that the need for top-down (dlPFC) adjustment of striatal value representations increases with BMI, whereas the interplay of self-monitoring (dmPFC) or eating-related strategic action planning (caudate) and salience processing (amygdala) might be hampered with high Disinhibition.International Journal of Obesity accepted article preview online, 17 February 2016. doi:10.1038/ijo.2016.28.