Plot of the fat fraction as a function of 1/density for Caucasian + Black + Hispanic males ages 18 to 31 (top), 32 to 50 (middle) and 51 to 89 (bottom). The black line is the optimal least square linear fit to the data. The other lines are predictions using the the Siri I (eq. (13), blue), Siri II (eq. (14), red) and Brozek (eq. (15), green) relations.