The roles of negative affect and emotion differentiation in the experience of 'feeling fat' among undergraduate students: An ecological momentary assessment study.

'Feeling fat' is the somatic experience of being overweight not fully explained by objective body mass. According to the body displacement hypothesis, 'feeling fat' occurs when diffuse negative emotions are projected onto the body in lieu of adaptive emotion regulation. Emotion differentiation, the ability to experience and label discrete emotions, is an important skill for adaptively addressing emotion that may reduce 'feeling fat.' We hypothesized that individuals with better negative emotion differentiation would be less likely to report 'feeling fat' when experiencing high negative emotion. We collected ecological momentary assessment data from 198 undergraduate students (52.24% female). Multilevel modeling revealed that both within-person increases in negative emotions and the tendency to experience greater negative emotion were associated with greater 'feeling fat.' Of the specific types of negative emotion, guilt and sadness predicted 'feeling fat.' Contrary to hypotheses, individuals with better emotion differentiation were more likely to report 'feeling fat' after experiencing elevated negative affect. These findings contradict the primary clinical conceptualization of 'feeling fat,' suggesting that factors beyond displacement of negative emotions onto the body may be responsible for 'feeling fat'. Results in a sample with pronounced shape/weight concern may better support the traditional clinical understanding of 'feeling fat.'