The relation of traditional and developmental measures of weight suppression to brain reward responsivity in bulimia nervosa
Authors:   , Singh Simar , Lowe Michael R. 
Published: July 2022

Objective: Although traditional weight suppression (TWS), the difference between one's current weight and highest past weight, has demonstrated numerous associations with eating pathology and prognosis among those with eating disorders (EDs), a simple subtraction of weights may be too crude. Developmental weight suppression (DWS), calculated as the difference between one's current BMI z-score and highest premorbid BMI z-score, was recently proposed to address this shortcoming. However, given its relative novelty, DWS remains to be validated across biobehavioral correlates of bulimia nervosa (BN). Our primary aims were two-fold: (1) to extend previous methodology (Singh, 2021) to explore whether DWS is related to reward-related brain responsivity to anticipatory and consummatory food cues among women with BN and (2) to examine whether DWS is more strongly related to reward-related activations compared to TWS. To understand how this might related to bulimic behaviors, our secondary aims were to examine whether objective binge episodes (OBEs), self-induced vomiting episodes, and restriction were correlated with: (1) each measure of weight suppression and (2) reward-related brain activation to anticipatory and consummatory food cues. Methods: Twenty women with BN underwent fMRI scans. Using the Burger-Stice taste paradigm (2011), participants were shown an image of either a glass of milkshake or water (i.e., anticipatory food cues), followed by delivery of the corresponding beverage via gustometer (i.e., consummatory food cues). Regression analyses were conducted to examine the association between DWS and brain activation, and bulimic behaviors and brain activation. Fisher r-to-z transformations were conducted to examine the strength of associations between brain activation and TWS vs. DWS. Finally, correlational analyses were conducted to examine the relation between each measure of weight suppression and bulimic behaviors. Results: Upon anticipation of milkshake vs. water, there were significant, negative correlations between DWS and activation in the right dorsolateral prefrontal cortex (dlPFC) and right precuneus (all p's < .01, k's > 50). Upon consumption of milkshake vs. water, there was a significant, negative correlation between DWS and activation in the right midbrain (p < .001, k = 70). Neither measure of weight suppression (WS) significantly differed from the other in its correlations with either anticipatory or consummatory brain activations (all p's > .01, k's < 50). Behavioral analyses revealed that TWS was significantly correlated with OBEs, purging episodes, and restriction over the past month (all p's < .05); in contrast, DWS was not significantly associated with any bulimic behaviors (all p's > .05). Upon anticipation of milkshake vs. water, frequency of OBEs, purging episodes, and restriction over the past month were all positively correlated with activation in the left amygdala (all p's < .001, k's > 333). Restriction was additionally correlated with activation in the left thalamus (p < .001, k > 378). Upon consumption of milkshake vs. water, frequency of OBEs, purging episodes, and restriction over the past month were all positively correlated with activation in the right dlPFC, right orbitofrontal cortex, left anterior prefrontal cortex, right caudate, and left anterior cingulate cortex (all p's [less than or equal to] .001, k's > 333). Discussion: Results support the notion that TWS and DWS are distinct measures of WS, with different relations to the biobehavioral correlates of BN. In general, greater DWS was associated with decreased responsivity to both anticipatory and consummatory food cues. In a novel finding, a three-way correlation emerged between TWS, bulimic behaviors, and activation in the right caudate and left ACC. Although further research is needed, this suggests a possible mechanism by which TWS maintains bulimic psychopathology. Future interventions should target TWS as a risk and maintenance factor for BN in treatment.