Neural Correlates of Weight Suppression and the Interaction with BMI among Individuals with Anorexia or Bulimia Nervosa
Authors:   , Willner Leora Benson , Lowe Michael R 
Published: December 2022

Anorexia nervosa (AN) and bulimia nervosa (BN) are eating disorders (ED) associated with a range of serious mental and medical health issues. They are often difficult to treat. A better understanding of neural factors underlying ED psychopathology could contribute to ultimately improving treatment outcomes. Weight suppression (WS), defined as the difference between highest past and current weight, has been associated with ED symptomatology and future weight change, but the mechanisms of action are still unclear. Further, WS often interacts with current weight or BMI to further influence ED psychopathology and weight change. Here we examine reward and inhibitory neural correlates of WS and of the interaction between WS and current BMI in a transdiagnostic sample of individuals with AN or BN. Participant ED status, weight history and current BMI were assessed at baseline. Participants then underwent functional MRI scanning while viewing short video clips depicting imminent food consumption while being told to either crave the food or resist the food temptation or depicting use of a neutral non-food item. After three months, weight change in these participants was also measured. Analyses were run using the traditional measure of WS (TWS), as a difference in pounds. However, because most individuals with disordered eating reach highest past weight during adolescence when growth is still underway, we also ran analyses using a developmentally sensitive WS measure (developmental weight suppression or DWS), as a difference between highest premorbid and current z-BMI, which accounts for age, height, and sex. Greater activation was found for the superior frontal gyrus (SFG), middle frontal gyrus (MFG), anterior cingulate cortex (ACC) and insula when contrasting resist food vs. neutral, crave food vs. neutral and resist food vs. crave food cues. Multiple regression tests found that the interaction between TWS and current BMI was associated with SFG, ACC and insula response to crave food vs. neutral cues, and with SFG, MFG, ACC, and insula response to resist vs. crave food cues. The interaction between DWS and current z-BMI was associated with SFG and insula response to crave food vs. neutral cues, and with ACC and insula response to resist vs. crave food cues. Interaction plots revealed that for all the regression tests those with high TWS or DWS (one standard deviation above the mean) had positive associations between BMI or z-BMI and brain response to crave food vs. neutral cues and negative associations between BMI or z-BMI to resist vs. crave food cues. Those with low TWS or DWS (one standard deviation below the mean) tended to show a relationship in the opposite direction. Responses of the SFG, ACC and insula to crave food vs. neutral cues were negatively related to weight gain at follow-up, and response of the MFG to resist vs. crave cues was positively related to weight gain at follow-up. The consistent patterns of findings were compatible with prior evidence from this dataset that found that the interaction between TWS and BMI and between DWS and z-BMI predicted weight change at three-month follow-up. Overall, in a sample of individuals with EDs, the association between current weight status and inhibitory and reward motivational response to food cues was moderated by weight suppression. This was the first study to examine neural correlates of WS and its interaction with BMI, and results suggest that neuroimaging holds promise in identifying brain mechanisms that underlie the interactive findings, including those on the associations with future weight change.