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What are the statistics on the density of our bodies? I.e. Mass/volume with full lungs. Does it follow a normal distribution like height and what is the mean and standard deviation?

In particular, how rare is it to be denser than water? I didn't realize it was possible to be denser than water until I met someone who literally sinks all the way to the bottom on a full breath of air.

  • The main factor that determines the body density is the amount of body fat. I don't think there are any other major factors, because the same organs should have about same density in different people (this can be affected by the amount of fat in the organs, but this usually goes along with the whole body fat). I'm not sure if anyone has measured the density of so many people that he could make a statistics out of it. – Jan Jul 22 at 16:25
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    Please clarify what you mean by density. That's not a measure normally applied to humans. Do you mean body fat percentage? – Carey Gregory Jul 22 at 22:33
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    @CareyGregory, he means density as it is understood in physics: mass per volume. He basically wants to know how many people are denser than water so they sink in water. A lot of people, including me, sink in water after breathing out air from the lungs. On the other hand, most people with air in the lung probably float. Fat is less dense and muscles and bones are more dense than water, so either a very skinny or very muscular person with little fat could sink. – Jan Jul 23 at 9:55
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    @Jan I want OP to say what he means and do so in the question. – Carey Gregory Jul 23 at 14:16
  • This question should be simple. It should be asking about body fat percentage since that's how density is measured in humans as @Jan explained in the first comment. I suspect if you quit searching for density and started searching for body fat % you would find the stats you seek. – Carey Gregory Jul 25 at 1:04
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Insulin Resistance, Body Weight, Obesity, Body Composition, and the Menopausal Transition (ScienceDirect, 2000)

Because bone and muscle have greater density than water, a person with a larger percentage of fat-free mass will weigh more in the water. Conversely, a larger amount of fat mass will make the body lighter in the water.

The density of:

  • Water (in the swimming pool) = 1.0 kg/L (source)
  • Adipose tissue (body fat) = 0.92 kg/l (source)
  • Muscle = 1.06 kg/L (source)
  • Bone (cortical) = 1.85 kg/L (source)

Things that are less dense than water will float and those that are denser will sink. So, who may sink in water even without breathing out air from the lungs: the one with little body fat, a lot of muscles and strong (thick) bones. To know "how many people" would sink, you would literally need to measure their body density (by underwater weighing or hydrodensitometry - see the first link), because it does not seem realistic to calculate this. Height/weight ratio and body fat percentage alone also do not help.

  • Thanks! Do you think it would be sensible to find averages for body water/muscle/bone content and then treat body fat as variable and use the statistics for that? Or are differences in bone/muscle percentage not negligible compared to body fat differences? – Zaz Jul 28 at 10:39
  • @Zaz By water density, I meant water in the swimming pool. In the human body, water is usually a part of organs and does not really appear as free water. Bone and especially muscle mass percentage differences are not negligible: a bodybuilder can have 10 kg more muscles that an average person. – Jan Jul 29 at 16:15

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