Only one in ten of the cells in your body is human. The other 90% are bacteria—we have about a 100 trillion of them on us and in us. The human colon is considered the most biodense ecosystem in the world. We’re just like along for the ride. We exist as one big superorganism, in a mutually beneficial symbiotic relationship—usually.
Collectively, our gut bacteria weigh as much as one of our kidneys and are as metabolically active as our liver. They affect our immune system —we just found out that if you give probiotics to kids, they don’t get sick as much. Our gut bacteria affect our hormonal balance, and they can affect our energy balance, as well. Is obesity linked to our gut flora?
There are some species of bacteria better at extracting calories from our feces than others. Pooped calories end up in the toilet rather than on our hips. But there’s certain obesity-associated bacteria with an increased capacity for energy harvest. Our bodies are trying to get rid of fecal matter, but certain bacteria in our colon can take our waste, break it down further, and release calories that are then absorbed back into our blood stream. So here our body is trying to get rid of it all and the calories are bouncing right back.
Now this was originally all based on mouse studies so we really didn’t know what to think, but finally this year we have some human data and indeed the type of bacteria in our guts is related to body weight and weight gain.
That got some researchers in Austria thinking. Maybe one of the reasons vegetarians are so much slimmer, on average, is because their diets foster more of the lean-type bacteria, rather than the obese-type.
And that’s exactly what they found. They took a bunch of fecal samples from vegetarians, did some DNA fingerprinting, compared it to… omnivore feces and found significantly more of the lean-type bacteria, suggesting a smaller capacity for energy gain from food in vegetarians. How much smaller? Perhaps 2% of daily caloric intake. That doesn’t sound like a lot but it just happens automatically—while we sleep even, and adds up over time. Over a year that may come out to about 5 pounds of fat. And that may not sound like a lot either but that’s exactly how much people tend to put on annually during mid-life years, so that could help explain why as we’ve gone over before, those eating vegetarian don’t seem to get that age-related weight gain that afflicts the rest of the population.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by veganmontreal.
To help out on the site please email firstname.lastname@example.org
Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other videos on weight loss. Also, there are 1,686 other subjects covered in the rest of my videos--please feel free to explore them as well!
For some context, please check out my associated blog post: Boosting Gut Flora Without Probiotics.
If you haven't yet, you can subscribe to my videos for free by clicking here.