Firmicutes makes you fat.  Bacteroidetes keeps you skinny like a baseball bat.

“Adiposity index” refers to the ratio of one line of bacteria, Firmicutes, to another line, Bacteroidetes, in your gut.  They say:  If Firmicutes is higher, you’re more likely to be obese.  If Bacteroidetes is higher, you’re more likely to be lean.  Yes.  Really.  (Take your pick of pronunciation.  I was taught Fir-mik-you-teez and Back-ter-oid-eh-teez.)

Research stuff:  Pretend you’re a mouse, created by researchers with a germ-free gut.  The researchers inoculate your gut with bacteria from an obese human who has higher levels of Firmicutes-type bacteria.  You now have Firmicutes in your gut.  Even though they keep your chow rations the same, you gain weight!  Your brother is a mouse with a germ-free gut, too, and they inoculate your brother’s gut with bacteria from a lean human who has higher levels of Bacteroidetes and lower levels of Firmicutes.   On the same chow rations as you, he stays a lean, mean, eatin’-machine.  Yes.  Really.  I know.  Your doctors just can’t believe you’re not sneaking Twinkies.

(There is more to this experiment, and it is interesting and leaves some questions.  The researchers put an obese-flora inoculated mouse and a lean-flora inoculated mouse in the same cage.  Mice eat each other’s poop, and so the floras were spontaneously able to be cross-inoculated.  The lean-flora predominated!  The obese-flora mouse should have gotten fat; it did not because the lean flora it yummily ate was able to “take over” in its gut.  The obese-flora was not capable of seeding itself in the gut of the lean mouse over the lean flora.  So both mice types stayed lean.  They took the experiment a step further, and changed rations to reflect a low-fat/high vegetable matter or high saturated fat/low vegetable matter (pizza pellets, for example–nice choice).  With the “bad” food, the obese flora persisted and the lean flora didn’t come in and overtake. This is where I look forward to seeing them isolate variables better in the future:  dairy fat, saturated fat with typical carb intake, saturated fat with low carb intake, no grain, and etc).

The amazing thing here is defiance of a cherished euphemism.  “Calorie in, calorie out.”  Calorie in, calorie out?  No.  Not quite a pure picture.  However, we can’t lie to ourselves.  It is still a pretty good picture, just not quite so clear.

Metametrix’s GI Profile Adiposity Index

The Metametrix 2100 Gastrointestinal Function Profile reports the “adiposity index.”  Basically it seems they just report your percentage of Firmicutes and Bacteroidetes with regards to each other.  My Firmicutes was 67 and my Bacteroidetes was 33 (67+33=100%).  I couldn’t find a ratio or percentage of ideal that I can quote.  Thought I saw somewhere 2:1, but I couldn’t re-find it.

Firmicutes and Bacteroidetes are phyla of bacteria (phylum, order, class, genus, species).   In the Firmicutes phyla are many that you know:  Clostridia, Streptomyces, Lactobacillus, Mycoplasma, and Bacillus.  In the Bacteroidetes phyla are  Bacteroides and Prevotella.  “Hey,” you say, “those are the bacteria reported in the Predominant Bacteria section of the Metametrix GI Profile.”  Yes, you are right.  It’s kind of a regrouping and refocusing of information.  Most all of the bacteria in the gut fall into either Firmicutes or Bacteroidetes.

I’m not sure what the adiposity index on Metametrix really helps with.  Or knowing the ratio of your Firmicutes to Bacteroidetes.  You know your body habitus.  It sounds like that may be enough for you to report your own index.  The best way to eat is to rely on whole foods (apples, oranges, bananas, raisins, broccoli, cauliflower, carrots, squash, pork chops, chicken, turkey, almonds, walnuts, olive oil, and I could go on–I’m just trying to prove that there is a lot to eat) and not packaged 100-calorie snack packs from Nabisco that I used to pop in my lunch box.

Back to the Skinny of the Matter

Firmicutes-type bacteria can actually metabolize more of your food and thus make more calories available to your body, making you gain weight.  They also stimulate the uptake of fat and may do something to your fat cells to make you store more fat.  More calories are absorbed, whether they be fats or carbohydrates you just ate.  The more you eat, the more weight you gain, the more Firmicutes-type bacteria you appear to get.  Firmicutes levels are able to be decreased:

• Firmicutes decrease with fasting, as Bacteroidetes increases
• Firmicutes decrease with weight loss.

I was very excited to share this information with my husband.  He has firmly stood by “calorie in, calorie out” in all of our debates.  Now he has nothing to stand on.  On the other, he is right.  We do need to be aware of empty-calories and ditch them.  Overall, it does have to do with what we put in our mouths, much more than genetics or bacteria.  My family has a history of obesity, and with my carbohydrate reliance/processed food reliance, I would have followed in the path of those set before me over the next 15-20 years as my metabolism slowed down.

Please Learn More

If you don’t know about gut bacteria, you are behind the game.  Gut bacteria is being found to, maybe not determine, but certainly play a role in immunity levels, obesity (as mentioned above), mental health disorders, cancers, vitamin status, and much, much more.   Nowadays, blaming your body’s bacterial flora for your problems is maybe more popular than blaming genetics.  That isn’t right either; it is ALL a balance.

Probably the biggest impact factors on these gut bacteria are what we eat and antibiotics.   Eating foods that are just a step or two away from the way you’d catch or pluck them in the great outdoors has to be one of the best things you can do for you and your family’s health and well-being.  In the name of “healthy,” we were brought Splenda; Splenda has been shown to decrease the beneficial gut bacteria.

So, please, ditch the processed food in its processed box.  Stop the madness.  I know it’s more expensive and requires you to shop more.  What you save in allergy medicines, doctor’s appointments, missed days of work because you or your kids are sick, eating out, and processed soda/juice/junk food will probably catch up balance out over time.

Science and drug companies may muck around with ways to manipulate Firmicutes and Bacteroidetes, but the natural way still seems best.  Focus on a whole foods diet, shunning high-calorie foods with little or overly-repetitive nutrient density.  YOU CAN DO IT.

Terri

Sources:

http://www.nature.com/news/bacteria-from-lean-cage-mates-help-mice-stay-slim-1.13693

http://www.sciencedaily.com/releases/2012/09/120912125114.htm