Scientists are treating obesity in mice with fecal transplants. The transfer of stool, meaning billions of bacteria, from one animal to another is not news. Humans have undergone them. It is losing weight from germs that is amazing.

This is a Panchatantra animal moral story. It is a tale of something really small rescuing something really big. It speaks to the interconnectivity between all living things. It is about germs and humans.

Already doctors are treating recurring intestinal infections with the transplantation of billions of bacteria from one person to another. Now scientists are treating obesity in mice with stool transplants, as reported in the New York Times on March 27.

The transfer of stool, meaning billions of bacteria, from one animal to another is not news. Already taken out of the laboratory and off the experimental shelf, doctors who specialize in the gastrointestinal tract presently transplant feces between humans. Before everyone stops reading, wait, it gets better. Germs save lives.

Patients who carry the bacterium Clostridium difficile, or C. diff, in their guts are at risk for a slew of problems, the worst being fatal mega-colon and pseudomembranous colitis. C. diff has become a threat as we prescribe antibiotics to treat infectious diseases or to halt infections before they start.

We are repeatedly exposed to antibiotics, including ingesting them in our food. C. diff has the nasty habit of returning repeatedly because it propagates via spores that are resistant to traditional therapies.

Instead of throwing more antibiotics to kill C. diff, gastroenterologists are fighting back with billions of bacteria, and the bugs do all the dirty work. Feces are filtered and then transplanted into the patient either through a colonoscopy or a nasogastric tube. In the ensuing battle of survival, the good guys take over and crowd out the bad guys.

How does this relate to obesity? In a couple of lab mice, researchers cured their obesity with germs. It has been known for a while that the intestinal flora of people who are thin is different from the flora of the obese. If that is not strange enough, when a person switches from fat to thin or from thin to fat, the germs also change. These observations lead to this question: Do bacteria play a role in our epidemic of obesity?

To find that out, researchers first did a gastric bypass on a group of obese mice. On a second group they performed a sham operation: They did surgery without the bypass. These post-op animals were further divided into those that continued on their enriched diets and the others were given weight-reduction grub.

As is the case with humans who undergo the same procedure, the overweight mice that had the real operation lost weight and had a change in their microbial passengers. The germs in the controls, regardless of their two diets, remained the same. So did their excess weight.

They further recorded the difference in the types of germs in the newly sleek rodents. The bacteria changed with the operation and weight loss. The scientists next transplanted the fecal germs from the formerly obese bypass group into germ-free heavy animals. They lost weight without the operation.

One can imagine the implications. The ultimate experiment would be to give obese humans the germs from those who have lost weight via the operation.

All of this is possible because the diets we consume may promote certain species of organisms that facilitate obesity by changing the metabolism or liberate more calories for the body to absorb. They have even narrowed the search to four particular species that may be the culprits.

So before everyone goes out and buys a nasogastric tube, more studies need to be done. There is still the lack of understanding why this transformation happens. Some hypothesize that these calorie-promoting germs were an advantage when our ancestors had little to sustain them. Now we have too much.

It also gives more understanding about our diets today and how we promote bacterial growth. Could it be the sugar-drowning drinks and processed foods? The answer is yet to come.

For now, while we all await our stool transplants we might as well start exercising and eating fewer processed foods, fats, calories, sugar and fructose-tainted everything.

This may turn out to be a new version of the ancient Indian fable of the little mouse rescuing the giant elephant.

Joseph Cramer, M.D., is a fellow of the American Academy of Pediatrics, practicing pediatrician for 30 years, and a clinical associate professor of pediatrics at the University of Utah. He can be reached at [email protected].