In fact, it's quite a party down there! Most of the bacteria received an e-vite for your colon party shortly after you were born. A few others were invited later because of what you ate or where you went on vacation or where you lived. But no matter when and how they got there, they pretty much fall into two categories: The 'A-listers', those that you want at the party, and the 'party crashers', those that just cause trouble and you want them to mellow out or just leave. If the party crashers somehow gain control of the party, things go south resulting in pleasantries like diarrhea, constipation, or even colon cancer.
It used to be easy to decide who was an A-lister and who was a party crasher based on whether the bacteria kept your colon functioning healthy. But like science tends to do, it's become a bit more complicated. A few years ago, a study in mice showed that those without any bacteria in their colons (aka, sterile) grew up to be lean whereas those that had a whole bunch of bacteria grew up to be fat. A little bit more science happened and those mice with certain classes of bacteria turned out to be thinner than other mice with different bacteria (and it wasn't always the 'party crashers' that caused weight gain).
You see, bacteria survive down there by eating the leftover carbohydrate that isn't digested and absorbed into your body sooner (and in eating the carbohydrate, they produce methane gas...is this ringing a bell?) Some bacteria are better at eating up all of the leftover carbohydrate than others. By munching on the leftover carbohydrate, they liberate the calories that would have otherwise passed right on through into the bowel. More carbohydrate-eating bacteria = more calories in your body. Less carbohydrate-eating bacteria = less calories in your body. How many calories are we talking about? Not yet known.
So do obese people have certain bacteria in their colons that make it harder for them to lose weight and keep it off? Maybe. Several Dr. Dorks seem to think so and are trying to conduct the studies to figure it out. But it's a bit complicated by the fact that there are so many different species living down there. Chances are, it's not going to be just one that is responsible for weight gain or weight loss. And maybe there are certain bacteria that eat up a lot of carbohydrate (that might lead to weight gain) but are really good for reducing your risk for colon cancer? Alas, it's not going to be simple to figure this all out!
What is SHE to do? At this point, I would do absolutely nothing except use this information to impress your friends. Colon-Speak makes for great conversations at intimate gatherings. "Do bacteria or cockroaches rule the world...discuss".
I'll keep my readers (all 8 of you) posted on any new findings related to this. Should be an interesting few years to see how this all shakes out!