Here is a study on measuring waist circumference which found that in this study the waist measured 2.5 cm above the umbilicus was the best measure of abdominal fat.

http://tinyurl.com/n4nxn6j

This is maybe not quite on track topic wise- but why are pants sized with the "waist" measurement in mind? Waist = narrowest part of waist, of course, but most pants presumably aren't worn that high, rather closer to low stomach/hip. So how does it correlate when women are so many different shapes? Why not just measure the actual part of the body where the pant's waist will sit? Like men's (I think?) Never ever got that one. .