Research has shown that a high-fat, high-sucrose diet does more than pump unneeded calories into a body. It also changes the balance of bacteria in your digestive system. This balance can be changed in as little as twenty-four (24) hours.

This report was issued in the new journal Science Translational Medicine on Wednesday, November 11, 2009.

It has long been known that many different factors play a role weight gain:

• Genetics
• Physical activity
• Environment
• Food choices

But evidence also indicates that bacteria play a role as well. All mammals need bacteria to help convert otherwise indigestible foods into digestible form.

Most bacteria fall into two major phyla:

• Firmicutes
• Bacteroidetes

Past research had already shown that over-weight humans had higher levels of Firmicutes than Bacteroidetes. Lean humans higher levels of Bacteroidetes than Firmicutes. By analyzing the genomes of the both bacteria, researchers Dr. Jeffrey I. Gordon of Washington University in St. Louis and graduate student Peter Turnbaugh concluded that the Firmicutes were much more capable at digesting food that the body can't.

Animals that have a higher proportion of Firmicutes convert a higher proportion of food into calories that can be absorbed by the body, making it easier to gain weight.

Firmicutes Bacteria Transfer
To verify this line of research scientists transferred bacteria from obese mice into so-called gnotobiotic (animals with no bacteria) mice. These mice were raised in a bacteria free environment, meaning that they had none in their guts. Once the Firmicutes were transferred to these mice they gained more weight than controls. Both the control and the firmicute "infected" mice were fed the exact same diet.

Human Bacteria Transfer & Dietary Change
Gordon and Turnbaugh also used gnotobiotic mice fed a low fat, plant rich diet. This diet was fed to the mice for weeks before the next step and for a month afterward. Bacteria from human intestines were then transferred into these prepared gnotobiotic mice. After the bacteria were transplanted from a lean human donor, the colonies in the mice had a high proportion of Bacteroidetes and a low proportion of Firmicutes.

After one month of bacteria transfer and lean diet, the diet was changed to a high-sugar, high-fat diet. Within twenty-four hours the balance of Bacteriodetes to Fimicutes reversed. Over time the mice also grew fatter than the controls who did not receive the human bacteria.

Other studies have shown that Firmicutes are twenty percent more prevalent and bacteriodetes almost ninety percent less prevalent in obese patients being studied than health, average weight patients.

Bacteroidetes include three large classes of bacteria that are widely distributed in the environment, including in soil, in sediments, sea water and in the guts and on the skin of animals.

Firmicutes are found in a wider assortment of environments. They are resistant to extremely dry conditions can and survive temperature extremes.