I may get scheduled for body fat testing next week, and with the screwed up stuff I've been doing to my body, my weight keeps going up and down. I may end up having to cut water weight yet again to avoid an inadvertent DQ.

The body fat testing they do is the multi-point bioelectric impedance testing. I know such testing is easily skewed by hydration, nutrition, and other factors. I am looking to figure out how very low hydration would affect the results. I am inclined to think it would reflect a much higher body fat % than if I were fully hydrated.

edit: I am also having the air displacement testing (Bod Pod) done tomorrow, when I will be normally hydrated. I hear it is supposed to be more accurate, but it isn't "official" since it won't be done by Air Force personnel.

You are correct in that those impedance calculators will translate increased hydration to lower bf, since muscle holds a lot of water. Unfortunately I can't tell you how much your dehydration will affect your results. I'm wondering if there's a way to manipulate sodium to help you out. I'll try and look into it after my exam tomorrow.

The more resistance, the higher the fat. The more sodium, the lower the resistance.*

There you have it: the best way to pass a test proving your health is to eat french fries and drink no fluids for a couple days.


*I'm not a biology person, this is what I think I learned in 5 minutes on wikipedia.

So I've done some thinking about this, and I'm not sure what to recommend exactly. Sodium does help with conductance, but it'll only help with conductance of the blood, not muscle. Dehydrated muscles have high resistance from what I've gathered, and having excess sodium in your system may dehydrate them more. But, if your muscles are starved for glucose, and you eat copious glucose before hand, it may start replenishing the glucose in your muscle. This will cause some water from your circulation to get pulled back into the muscle. I also just read on wiki that eating a meal right before BF testing via bioimpedance will tend to underestimate BF%.

So I don't want to give you bad advice, but HYPOTHETICALLY, you'd want to eat a small, sugary, and salty meal about 30 minutes before your test.

Just a heads up, it appears that the Bod Pod is far less accurate (depending on it's calibration) than the initial reports that came out. Seen this both from personal & 2nd hand experience. From what I've heard (take it for what it's worth), calipers or water submersion are still the most accurate.