Gaps in Measurement: Highlighting Anti‐Fat Bias as an Underrepresented Construct in the Modified Weight Bias Internalization Scale

ABSTRACT Increasing cross‐sectional literature highlights a strong overlap of internalised weight bias (i.e., weight‐based self‐devaluation) with constructs like body dissatisfaction. The highest overlap is in studies that use the Modified Weight Bias Internalization Scale (WBIS‐M). We argue that anti‐fat bias (e.g., negative judgements of fat people) is a core feature of internalised weight bias definitions not represented in the WBIS‐M, making its items less distinct from body dissatisfaction. To investigate, we examined the longitudinal relationships of anti‐fat bias with internalised weight bias among 3025 sexual minority men using random intercept cross‐lagged panel models. We contend that, if the WBIS‐M adequately captures anti‐fat bias, these constructs should be strongly associated across time. To the contrary, we found medium cross‐lagged (longitudinal) relationships of these constructs over time ( β s 0.07–0.08), and a small between‐person association of these constructs ( β = 0.10). The limited strength of these effects suggests that the WBIS‐M does not adequately capture anti‐fat bias to the extent that existing definitions suggest it should. Researchers must be cognisant of what measures capture, and consider what scales most appropriately capture the components of weight stigma they want to assess.