"Feeling fat" is the subjective sensation of being overweight, which is not fully explained by one's body weight. Disruptions in emotion differentiation and gastric interoception may contribute to feeling fat. We hypothesized that poor negative emotion differentiation and poor gastric interoceptive accuracy would each be associated with higher levels of feeling fat after adjusting for negative affect intensity and body fat percentage. Cisgender female university students (N = 69; M(SD) age = 20.3(3.7), 60.9 % heterosexual, 91.3 % white) completed questionnaires and the two-step water load test. Regression analyses, which adjusted for negative affect intensity and body fat percentage, found that neither negative emotion differentiation (B < 0.001, p = .52) nor gastric interoceptive accuracy (B = 0.01, p = .97) were related to feeling fat. Post hoc, eating pathology severity moderated the relationship between negative emotion differentiation and feeling fat (B = -6.97, p = .03); poorer negative emotion differentiation was associated with greater feeling fat for those with Eating Disorder Examination Questionnaire Global Scores above 1.47 (B = -5.79, p = .050). The relationship between gastric interoception and feeling fat did not vary by eating pathology severity (B = -0.04, p = .79). Self-reported feeling full also contributed to feeling fat after consuming water to perceived maximum fullness (p < .001); however, changes in feeling full were not associated with changes in feeling fat across the task (p = .09). Poorer negative emotion differentiation is associated with feeling fat for those with elevated eating pathology. Individuals with elevated eating pathology may benefit from improving their ability to label and understand emotions to reduce feeling fat. Future research should test whether changes in feeling full cause feeling fat.
