Suppose that a bodyfat percentage for about 12% for males, and about 24% for females is required for visible abdominal six-packs. How rare are visible abdominal six-packs?REWRITE: Andy Lemke and Andrew Koenigsberg were right in that I originally misread the question. So, let me start of by first qualifying what most people would consider to be six(6)-pack abs. In the photos by Marlene Dempster, the men have clearly defined sets of abdominal muscles. That is to say, without going into too much anatomy, that not only is the entirety of the abdominal section outlined, but so is each of the six muscles (plus the surrounding muscles) that make up the abs which we all consider essential to a 6-pack.
Now, that said, I was told before that in order to show such definition in the abdominal region, you need to be at about 5% body fat. That number tends to vacillate between phenotypes, but the majority of the Q&A sections I checked had a consensus of "about 5% body fat", so I'll stick to that. So then, now comes the actual question: How much of the country has 6-pack abs? I can't say for sure. I can, however, make an educated guess based on the following:
I found a map of the country's BMI distribution as of 2009 and am extrapolating back from that: http://apps.nccd.cdc.gov/DDT_STR.... Also, a 2011 statistic regarding the average weight and height of males and females in the US is here http://www.cdc.gov/nchs/fastats/....
By the looks of the maps, about 3-5% of the entire US population could be considered within the range of having 6-pack abs. Chances are that it's even less than that, however, as BMI doesn't translate very well to body fat %. Even then, I assumed a standard Gaussian distribution of the BMIs and went about 3-4 standard deviations from the average to find the 'eligible' people.
Unfortunately, there is some kooky conversion scheme to get between body fat and BMI - Body fat % = ((BMI * 1.2) + (Age * 0.23) - 16.2) . Note that the 16.2 value is for males. For females, the number is 5.4. I do not know why. Now, the reason I don't agree with this is because I have a body fat percentage between 9 and 10%, but a BMI of 21.4. According to the above equation, I have a body fat percentage of 14.29%. Using this formula, I would have to have a BMI of 13.2583 to reach 5% body fat. That doesn't make sense to me, so I'm considering anyone with a BMI of 18-20 to be 'eligible' for having a 6-pack.
Note: This method breaks down when you consider people who are, say, my height, and heavily muscled, like a body-builder. His BMI would be much larger than mine, but his body fat % would be less. Still, I tried.