The claim that bacteria in the human body outnumber human cells by an order of magnitude or so has become a popular observation among Science Fans. A 2008 article in the ghastly New York Times states:
The bacterial cells also outnumber human cells by 10 to 1, meaning that if cells could vote, people would be a minority in their own body.
This is misleading. A single bacterium masses something on the order of 10-13 – 10-12 grams, while a human body cell is in the neighborhood of 10-9g — 1,000 to 10,000 times larger. By weight, bacteria therefore compose somewhere between 1% and 0.1% of you, depending mainly on how recently you went to the restroom. Thus, the Important and Popular Fact presented in the NYT and other sources is technically true*, in the sense that Vin Diesel is outnumbered by a small bag of crickets.
*: The claim also skips over the fact that the largest fraction of the bacterial population in question consists of symbiotes, which could be designated honorary human cells under the mitochondrial grandfather clause, but that’s a whole other post.