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Thank you James for your excellent article on bodyfat measurement methods. I used 2 DEXA scans on me in one week. Both on Mondays using the same routine each time(exersice, food, time of the exam and I believe hydration) and with the same machine operated by the same technician. My bodyweight in my first exam was 117kg with 180cm height and my BF% according to the DEXA scan was 42,1%. On the following Monday my measurements where: 114kg with no lean mass loss but with increased BF% 42,6% ! In this week I followed two vey popular weight loss systems.… Read more »
Thank you for the thorough, well-researched summary. This is the most valuable collection of information on the subject available. Regarding your advice to take measurements less frequently when the error rate is high, my intuition would tell me to do just the opposite. Whether a measurement has errors due to inconsistency or a consistent bias, I would expect that more frequent measurements, plotted on a chart, would be the best way to show the true trend, and allow you to make adjustments to your diet and exercise. What I do is use my body fat scale every day and plot… Read more »
Thanks for your comment, Rob. Yes, I can see what you are getting at with more frequent measurements, and taking the average of those measurements. This can be beneficial to people who see the “big picture” like you do. However, for people who get hung up on specific day-to-day numbers, this method could be detrimental psychologically. So it really depends upon the person.
I have always sensed that weight loss measured on the scale tends to lag fat loss as inferred from changes in my body circumferences and skin fold thicknesses. The calipers are a useful tool. I would like to invent electronic underwear that gives me the answer more quickly and accurately.
Judith,
Body weight is heavily affected by factors such as water retention, while body circumferences and skinfold thicknesses aren’t as heavily impacted by these. This is probably why you sometimes notice a lag between the two. Of course body circumferences and skinfolds can have their limitations as well, and it is critical that the same person is doing the measurement each time with an identical technique.
Thanks james
What are your thoughts on ultrasound testing? They just use a wand similar to what they use for pregnant women on up to seven skin fold sites.
The data on ultrasound indicates that it has roughly equivalent error rates to calipers.
I’m somewhat curious that you suggest that the only way to accurately tell your body fat percentage is to strip your body down and weigh each of the component parts. How then can you tell how much error there is in the methods you examined, considering there is no true baseline to compare it to? I’ve had a few DEXAs done over the past couple of years, and the total body weight the DEXA machine gave for me has always been less than 1% variation of the scales. For a tiny beam of x-ray to be that close, surely that… Read more »
When you say 4-5% error rate, does that mean 4-5% BF or 4-5% of the total?
For example I had DXA put me at 8.1% BF. Would it then be 7.6-8.5% (4-5% either way) OR
3.1-13.1% BF?
Thanks!
I mean 4-5% BF.
So If DXA has you at 8.1%, the true range would be 3.1 to 13.1 (although in that case, the lower end is highly unlikely).
I am curious. Has there been any study that established sort of a working conversion between waist hip ratio and body fat percentage. For example a waist hip ratio of 0.8 for male is equivalent to ?certain level of bodyfat percentage
I want to thank you for saving me $49 ! I had a DEXA scan done in May 2009 and was pretty disappointed to be told that I was 29.7% fat. The likely hood of my building 10 lbs of muscle are pretty slim! And it is highly unlikely that I will lose 10 pounds of PURE FAT and then maintain a BMI of 21. It was depressing to realize that a body fat percentage of nearly 30% (thus practically “obese”) was my lot in life. I’ve been toying with the idea of having another (since I think, MAYBE I’ve… Read more »
Thank you, Denise! Glad you liked the article. Yes, you are welcome to put a link on your page!
I disagree with #3. I have developed a measurement method that I perform on myself every month or so and it is very sensitive to changes in body density. I am talking about changes only here, not the absolute fat% value. I agree with you about the percentage fat being inaccurate and that number is of less value to me anyway. I measure my own weight hydrostatically. I practiced exhaling to my minimum residual lung volume, until it became very consistent (many sessions over a month long period). Then, I used empty bottles of various sizes as buoys and determine… Read more »