Our scales use the Bioelectrical impedance analysis (BIA) method. It sends a tiny current allowing us to measure your impedance which can then be used to calculate an estimate of total body water (TBW). Total body water (TBW) can be used to estimate your lean body mass. By subtracting your lean mass from your body weight it can also estimate your body fat.

Note that:
Fat mass + Bone mass + Muscle mass = 100% of your body composition = Your weight
As there is water in muscle and fat, the water mass cannot be added to the other metrics when calculating the body composition.

Important: Withings has not evaluated the accuracy of the measurement in patients with scar tissues, so Withings cannot guarantee that scar tissues do not have an effect on the accuracy of the measurement in a population of patients with scar tissues.

However Withings is not aware of any contraindication to the use of bioimpedance in the presence of scar tissues. In addition, it does not seem probable that scar tissues will affect the accuracy for a couple of reasons:

1. The scar tissues are made of collagen fibers as normal skin. The difference is in the orientation of the fibers, which should not have an impact on the bioimpedance measurement.
2. The electric signals used in a bioimpedance measurement propagate deep into the tissues, so that they should not be significantly affected by modifications of the composition of superficial tissues, if any.