. ▁Since ▁the ▁advent ▁of ▁the ▁first ▁commer cially ▁available ▁devices ▁in ▁the ▁mid - 1 9 8 0 s ▁the ▁method ▁has ▁become ▁popular ▁ow ing ▁to ▁its ▁ease ▁of ▁use ▁and ▁port ability ▁of ▁the ▁equipment . ▁It ▁is ▁familiar ▁in ▁the ▁consumer ▁market ▁as ▁a ▁simple ▁instrument ▁for ▁estim ating ▁body ▁fat . ▁B IA ▁actually ▁determ ines ▁the ▁elect rical ▁imped ance , ▁or ▁opposition ▁to ▁the ▁flow ▁of ▁an ▁electric ▁current ▁through ▁body ▁t issues ▁which ▁can ▁then ▁be ▁used ▁to ▁estimate ▁total ▁body ▁water ▁( TB W ), ▁which ▁can ▁be ▁used ▁to ▁estimate ▁fat - free ▁body ▁mass ▁and , ▁by ▁difference ▁with ▁body ▁weight , ▁body ▁fat . ▁ ▁Acc ur acy ▁ ▁Many ▁of ▁the ▁early ▁research ▁studies ▁showed ▁that ▁B IA ▁was ▁quite ▁variable ▁and ▁it ▁was ▁not ▁regarded ▁by ▁many ▁as ▁providing ▁an ▁accurate ▁measure ▁of ▁body ▁composition . ▁In ▁recent ▁years ▁techn ological ▁improvements ▁have ▁made ▁B IA ▁a ▁bit ▁more ▁reliable ▁and ▁therefore ▁more ▁acceptable ▁way ▁of ▁meas uring ▁body ▁composition . ▁Nevertheless , ▁it ▁is ▁DE X A ▁and ▁M RI ▁- ▁and ▁not ▁B IA ▁- ▁that ▁are ▁regarded ▁as ▁the ▁reference ▁method ▁in ▁body ▁composition ▁analysis . ▁ ▁Although ▁the ▁instruments ▁are ▁straightforward ▁to ▁use , ▁careful ▁attention ▁to ▁the ▁method ▁of ▁use ▁( as ▁described ▁by ▁the ▁manufact urer ) ▁should ▁be ▁given . ▁▁ ▁Simple ▁devices ▁to ▁estimate ▁body ▁fat , ▁often ▁using ▁B IA , ▁are ▁available ▁to ▁consum ers ▁as ▁body ▁fat ▁meters