I've been using the Navy Body Fat Calculation method for about two months in conjunction with an exercise regimen. It's done it's job as far as telling me that I'm loosing body fat and gaining lean muscle in it's place, but I still wonder how accurate it is and can be.
From everything I've read on the net, the general consensus is that it's accurate to within 3% of what Hydrostatic Weighing gives you, but I've noticed something about it's output, namely that my neck measurement has more of a (reverse) hold on what my BFP is than my waist measurement does.
If my waist measurement increases size 1/8th of an inch (which would indicate a gain of BFP), but my neck measurement increases by 3/8ths of an inch, then my BFP is calculated as losing .61 percentage points.
On the other hand, if my waist measurement stays the same (which indicates no change), and my neck measurement decreases by 1/2 inch, my BFP is calculated as gaining a half a percentage point.
I understand I'm being nit-picky here, as it is telling me that over the past two months I've lost about 4% (coming up on 5%) in BFP, but wouldn't my waist have more weight in the calculation of what my body fat is doing than my neck? The way it is now it seems kind ass backwards, pardon the french.
Was this built into the Navy algorithm? Does this make it inaccurate?