  Smart weight scales offer bioimpedance-based body composition analysis as a
supplement to pure body weight measurement. 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. Our paper combines transgender
studies-influenced personal narrative with an analysis of the scientific basis
of bioimpedance technology used as part of the Withings smart scale. Attempting
to include nonbinary people reveals that bioelectrical impedance analysis has
always rested on physiologically shaky ground. White nonbinary people are
merely the tip of the iceberg of those who may find that their smart scale 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 a rainbow flag on the packaging. We also provide
recommendations as to how to approach creating more inclusive technologies even
while still relying on exclusionary data.
