A pubmed hit search teaches us that Human Body Composition (BC) is a frequently used issue in nutrition publications. Body composition is a branch of human biology and is subject to variable interpretation by its users. Quantifying human BC plays an important role in monitoring health and disease but inaccurate interpretation of terms and techniques plays a key role in a series of classical errors. The purpose of this study is to make an overall review of general and specific errors that occur in BC e.g. in medicine and nutrition in particular. It was found that the transfer from morphological BC to chemical BC interpretations is the major origin of error. It all started with hydrodensitometry that for too long was “the” reference method, but being itself erroneous. This has caused different outcomes of methods assumed to measure the same variable producing the same outcome. More specific, it was found that the Body Mass Index as used in BC is a violation of biological evidence, while the new reference criterion DXA does make good predictions but is not accurate for individual patient evaluation or diagnosis.