do you need the body fat for further experiments? Otherwise the fastest, non-invasive method to measure body fat, lean, and fluids would be NMR-based, like Brukers minispec.
I agree completely. The fastest non-invasive means to measure fat mass is to use qNMR. We depended on the Echo system for years. There are caveats; fat mass is very accurate, but lean mass includes all soft tissue organs, not just muscle. Total body water was an unreliable measure for us. Other methods were better. You will find that adding all of these parameters together does not equal 100% as the skeleton is not included in that calculation.