Although body fat percentage is somewhat subject to error, it’s a useful measurement to have when accurately setting and adjusting macros.
The system uses estimated body fat as follows:
To calculate lean body mass (LBM), which is used to set your protein target. Also known as" fat-free mass," LBM includes bone, connective tissue, glycogen, organs, blood, and water (everything but fat). The greater your LBM, the more protein you’ll need.
To adjust your macros at each weigh-in. Although your change in weight is the main measurement used to determine whether your macros are working, the system also considers your change in body fat.