The percentage fat is calculated using the Gallagher (2000) equation which is based on the age,
sex, ethnicity and Quetelet body mass index.
The classification is taken from the same research which identified the percentage body fat
that approximates to the WHO BMI thresholds.
The widely quoted thresholds for defining obesity from percentage body fat of 25% for males
and 30% for females correlates poorly with conventional BMI definitions and is effetively a
much lower threshold for diagnosing obesity.