According to a renowned leaker, Samsung has equipped the Galaxy Watch 4 or Galaxy Watch Active 4 with a sensor that could help people track their body weight. Apparently, the South Korean company has integrated a BIA sensor in its next smartwatches, which will be capable of measuring your body composition.
https://www.notebookcheck.net/Samsung-Galaxy-Watch-4-tipped-to-feature-a-body-composition-sensor.547496.0.html