Our microbes, ourselves

It is becoming very clear that obesity is not caused by the weak-willed or McDonalds per say. It is becoming more clear that hormones and genetic predisposition is far more important. Take for instance gut microbes, that may well be the lead actor telling the person what to eat.

A new article notes that there is a "link between differing microbial populations in the human gut and body weight among three distinct groups: normal weight individuals, those who have undergone gastric bypass surgery, and patients suffering the condition of morbid obesity..."

What is living in your gut may well be dictating what you feel like eating.

Dr. John DiBaise, a gastroenterologist at the Mayo Clinic, Arizona, Bruce Rittmann, Ph.D., an environmental engineer and a member of National Academy of Engineering, Rosa Krajmalnik-Brown, assistant professor of civil and environmental engineering all worked on this study.

The team look at 16S rRNA, molecular structure which provides a characteristic fingerprint for microbial identification.
The team used:
454-pyrosequencing, which allows a significantly larger number and greater diversity of gut microbia to be identified.

"The resulting composition of gut microbiota in the three gastric bypass patients differed substantially...the microbial populations extracted from obese individuals were high in a particular microbial subgroup, hydrogen-producing bacteria known as prevotellaceae."

"Further, such hydrogen producers appear to coexist with hydrogen-consuming methanogens, found in abundance in obese patients, but absent in both normal weight and gastric bypass samples."

This is really amazing. This means that a certain bacteria appears only when you are obese. Not when you are not, or not any more.


"Organisms producing hydrogen and acetate create a situation like cars flooding onto the highway. The methanogens, which remove the hydrogen, are like the offramps, allowing the hydrogen cars to get off. That allows more acetate cars to get on, because some hydrogen cars are coming off the highway."

The bacteria that consumes the hydrogen and acetate are present only in the overweight. So that must mean that hydrogen and acetate must exist, and that the bacteria that consume it causes, via by their presence or by-product, the obesity.

Here is where is gets interesting.

"The methanogen offramps, by removing hydrogen, accelerate the efficient fermentation of otherwise indigestible plant polysaccharides and carbohydrates. The effect is to boost production of SCFAs, particularly acetate, which will be taken up by the intestinal epithelium and converted to fat. The result over time may be increasing weight, eventually leading to obesity."