The iHealth Core (HS6) measures all body parameters for people between 18 and 70 years old.
Under 18 or over 70 years, only weight and body fat are measured.
On the other hand, the bio-electrical impedance analysis (BIA) is difficult for people under 18 or over 70 years because of the rapid changes of the body specific to everyone. The fat mass measured for these people is a fat mass reference. In this case, it is preferable to focus on the curve of the evolution of the fat mass in order to see if it increases or decreases.
Menu > MyVitals > Tap on "Weight" graph > Look at "Body fat" graph
*credit to Sylvain of iHealth Labs EU
https://helpcenter.ihealthlabs.eu/hc/en-gb/articles/208061775-iHealth-Core-HS6-In-the-app-I-get-only-my-weight-and-my-body-fat-The-other-parameters-are-not-visible