Companies such as Withings and Fitbit tout composition analysis as providing self-knowledge and the ability to make more informed decisions. However, these aspirational statements elide the reality that these numbers are a product of proprietary regression equations that require a binary sex/gender as their input. In this talk, we’ll discuss results from a recent paper that combines transgender studies-influenced personal narrative with an analysis of the scientific basis behind the bioimpedance technology used as part of the Withings smart scale. Attempting to answer the question of how to include nonbinary people reveals that bioelectrical impedance analysis has always rested on physiologically shaky ground, with White nonbinary people being merely the tip of the iceberg of those who may find that their smart scales is not so intelligent when it comes to their bodies. Using body composition analysis as an example, we explore how the problem of trans and nonbinary inclusion in personal health tech goes beyond the issues of adding a third “gender” box or slapping on a rainbow flag on some packaging.