Why does the scale not tell the whole story on GLP-1?

The bathroom scale measures total mass, nothing else. It cannot tell you whether a five-pound drop is fat, water, glycogen, food in transit, or muscle, and on a GLP-1 it is usually a mixture. A scale-only view of an Ozempic, Mounjaro, Wegovy, or Zepbound run can hide a lean-mass loss that only becomes obvious on a DEXA report a year in. The scale also cannot show regional change, so it cannot tell you whether visceral fat is dropping or whether your legs are getting smaller because the muscle is going. Body composition tracking fills both gaps. In Phaze, weight, body fat percent, and muscle mass share one chart, so the scale stops being the whole story. The numbers are for information, not diagnosis.