“I’m not fat, I’m big boned.”
“I am overweight, because of my large bones.”
We might be quite familiar with such comments, but is there any truth to them?
First, take a moment and answer the following question. How many pounds do you think your skeleton weighs? 5 pounds? 10? 20? 40?
The DXA machine helped us to decipher if muscle actually weighs more than fat, and I think will help us answer the ‘big boned’ question.
The DXA estimates how much bone mineral we have in our entire skeleton, which we can convert to pounds.
Take these five, random scans of women I pulled from our lab’s DXA scanner. Their skeletons ranged from 4.9 to 6.2 pounds, which was only about 3 to 3.8% of their total body weight.
But are these women just outliers? Actually, no, they appear to be quite average, as compared to this large study of U.S. adults.1
These graphs are the bone mineral content for White, Black, and Mexican American women from 20 to 85 years of age. Each blue dot represents a person who was measured.
Their estimated skeleton weight averaged from about 3 to 4 pounds. In men, the average skeleton weight was about 5.5 to 6.5 pounds – with the heaviest skeletons being only about 11 pounds.
Personally, the largest skeleton I have scanned was a 350 pound professional football player, who had a 13 pound skeleton – still a mere 3.7% of his body weight.
In conclusion, this one is busted. We are not ‘big boned’, as the weight of our skeletons do not make a substantial contribution to our overall body weight.
Kelly, T. L., Wilson, K. E., & Heymsfield, S. B. (2009). Dual energy X-Ray absorptiometry body composition reference values from NHANES. PLoS One, 4(9), e7038.
X-Ray Image: From Keith Martin documentary. http://www.channel5.com/show/70-stone-almost-dead.