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Dehydration and body fat %


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I finished a 4 week fitness boot camp last week.  Unfortunately on the last day (Friday) we were supposed to have our final weigh-in, measure, and BF% taken to compare to where we were before we started, but I was really sick and ended up missing the last day.  I was in bed most of the day, vomiting, etc. and I didn't drink enough fluids so I know I was severely dehydrated.  However, that afternoon I started feeling better, so I figured I would still go weigh in that afternoon (silly me I figured I would weigh less after all the vomiting, LOL).  I HAD lost a lot of weight but she was showing my BF% had only gone down 1% and half of my weight loss was muscle instead of fat.  That freaked me out since I have been doing some major weight training and I don't see how I could have lost any muscle, let alone as much as she said. 

I have been monitoring what I am eating every day on CC and my diet has been really good with enough protein and nutrients, so I am very concerned if it is true that I lost so much muscle.  Obviously my goal was to lose fat, but GAIN muscle, not lose it!!

My husband was thinking maybe since I was dehydrated that threw off what the calipers were reading and maybe my BF% really isn't as high as she thought?  Is that possible?   I wish I could get checked again and see if it's changed now that I am hydrated, but it's not possible.

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My nutritionist told me that if you're dehydrated, the electrical BF test will definitely show you at a higher percent then you are, but I'm not sure if it effects calipers.

I'm going through the same thing that you are because I'm on a diuretic. My nutritionist's electrical machine showed me at nearly 30% BF. She said this confused her, she said, becuase I in no way looked like it.  (I'm 5'11 and 147lbs.)

Chances are that I'm dehydrated. I took my measurements accurately with a measuring tape and plugged them into this site, which said I have 18.3% body fat.

http://www.healthcentral.com/cholesterol/home -body-fat-test-2774-143.html

Hope that helps a little! Please don't fret. ^_^ With all of the work that you've been doing and the changes you've seen/how sick you were, it sounds like the measurements were wrong.
#2  
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Yes dehydration greatly affects the electrical body fat percentage tests.  So I wouldn't worry about your results.  If you're curious you can always buy one to use at home to measure it.  They're fairly cheap.  I wouldn't put too much stock in that website though, those are only based on what's true of the average person who shares your measurements.

I've got one of those Tamika scales which gives you the BF% percentage and hydration %, but I always assumed it was inaccurate so I never use it other than for weight.  I guess I could give it a try.

#4  
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from what I've read, they're within 1-2% accurate.

Cool, thanks!  I'll try it when I get home, then. 

Fuzzy, my understanding is that you cannot lose fat and gain muscle at the same time. The two are contradictory: Losing fat takes calorie cutting, while gaining muscle takes calories.

Also understand that whenever we lose weight, a certain percentage is going to be muscle. It's unavoidable. Weight training while calorie cutting can minimize just how much muscle is lost.

Finally, if she was using calipers it has nothing to do with your hydration level. BUT calipers are notorious for being wrong - they get uncalibrated easily, and you need to measure in just the right spot, etc.

A better gauge is:

1) Did your measurements change favorably?

2) Are you clothes fitting better?

3) Can you lift more weights than you did before?

As for the impedance scales, they aren't all that accurate. Females tend to read 7 points too high; men tend to read 4 points to low. That's a pretty big difference!

But I still like my scale anyway... esp since it's telling me I have the metabolic age of a 19 year old. Heh! ;-)


1) Did your measurements change favorably?  yes!  Lost 0.5 inch on each arm, 1 inch on each thigh, 2.5 inches on my waist, and 1.5 inches on my chest!

2) Are you clothes fitting better?  yep!  The pants are getting almost baggy.  If I lose much more i will have to go shopping!

3) Can you lift more weights than you did before?  yes!  I can also run longer!

So, she was saying my fat loss and muscle loss were about half and half - isn't that a pretty bad percentage?

The impedance scales are pretty good if you use them as a measure of change, rather than an exact measure of bodyfat. I've read that it's the second most accurate way of measuring bodyfat (after hydrostatic testing - where they dunk you in water and measure your volume). You do need to make sure that you measure at the right time though - the book that came with my tanita suggests just before dinner - it needs to be a couple of hours after eating, and at least a couple of hours after you wake up.

Fuzzy - depends on how much weight you had to lose to begin with.

If you have a lot of weight to lose, you can afford to lose more muscle. Think about it. It takes a lot of muscle just to carry around a lot of fat.

If you are near your ideal weight, then the story is different.

By your answers, I would have to say you have nothing to worry about - you're doing great! The "eyeball" test is much more accurate than any caliper or imedance test, in my opinion.

At my highest body fat, I am dehydrated - 30%

At my lowest body fat, I am very hydrated - 26%

I tend to believe my body fat is 26% and there is a direct correlation between hydration and body fat readings with electrical equipment.

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