As energy retention as a whole consists predominantly of protein and lipid, efficiency
can be determined for protein and lipid separately by using a multiple regression analysis,
as described first by Kielanowski (1965). Based on the above equation for DE intake
( y) and the same data base, a multiple regression can be established where both protein
and lipid gain (in kJ kg 0.80 day 1) are expressed as their energy equivalents using 23.1
kJ g 1 protein (x) and 35.8 kJ g 1 lipid (z) retention, respectively.