Bug-Brain-Waistline

Forget the screaming headlines and the infomercials – dieting, weight gain and weight loss are not simple matters. Did the faecal transplant received from a daughter make a Rhode Island woman ravenous, rapidly fattening despite liquid diets, exercise and strict medical supervision? Are the supplements sold everywhere as probiotics the answer to irritable bowel syndrome and inflammatory bowel disease or potential causes of illness? Do we really know how the gut and the brain interact, or is our present semi-hierarchical version of different organ systems (brain, GI tract, muscle) making us miss how information flows in the body?

Let’s take a look.

Keeping Things in the Family

In “Open Forum Infectious Disease” Neha Alang and Coleen Kelly of Brown University describe an unusual patient. She was first treated with antibiotics for a vaginal infection. She did not feel better. Instead she developed clostridium difficile infection or CDI – also diagnosed in a family member.  Though provoked by antibiotics killing lots of gut bacteria, CDI is itself scarily antibiotic resistant. It kills perhaps thirteen thousand people every year – just in the U.S.

Next our patient went on “standard” treatment for CDI – metronidazole. That failed. This was followed by vancomycin, the “gold standard” of treatment for two weeks. By then she had added a new infection of helicobacter pylori, the stuff that causes ulcers and stomach cancer. Next up  – a further twelve weeks of vancomycin. Two weeks after finishing that, diarrhea recurs. Now she’s given rifaximin with saccharomyces boulardii bacteria. Her H. pylori infection remains.

So antibiotics layered on other antibiotics – for months – leave her still infected. Not good.   Her doctors then gave her the most effective treatment for clostridium difficile  a fecal transplant – an infusion of stool to replace her own. But from whom do you get the right stool? Just as you might with a kidney transplant, the patient wanted a source she knew and trusted, right in the family.

She got the fecal translplant from her daughter – after another course of antibiotics to kill off the H. pylori.

This treatment worked. But the side effects were unexpected.

 The Weight Of Your Gut

Prior to her diarrheal disaster, the woman had shown a stable weight of around 134 pounds – which, slightly amazingly, stayed the same throughout antibiotic treatment. After the fecal transplant, however, she felt ravenous. A little over a year later, she gained 36 pounds, going from a body mass index of 26 to 33. Three years after the ordeal she weighted 177 pounds, and was chronically constipated.

Her daughter? A 140 pounds prior to providing her stool to Mom, she subsequently gained thirty pounds herself. Mom stayed quite adamant her desire to eat rocketed following the fecal transplant.

Why She Did Gain Weight?

Changes in bacterial populations certainly had something to do with it.

As the authors reported, treating H. pylori is known to cause weight gain. That bacterium can change the levels of ghrelin, one of the prominent hormones controlling food satiety. But both mother and daughter had not been obese prior to the fecal transplant. Both – now with presumably similar bacterial populations – quickly got fat.

Is there evidence to support bacteria change people’s weight? Sure. It works that way in animals. Obese humans have notably different bacterial populations than slim ones.   But what’s doing what?

Brain and Bacteria

Consider this: 1. Changing bacterial populations are related to people’s moods 2. Viral infections – as with adenovirus – can cause weight gain 3. Woman who harbor more toxoplasma parasities in their blood – usually obtained from local cats – are more prone to suicide 4. The gut, also known as the “second brain,” has a lot more serotonin than the brain – one possible reason many antidepressants but symptoms and weight. 5. People with irritable bowel and esophageal dysmotility have very high rates of depression and anxiety problems.

So pointing a finger at the fecal transplant as the cause of this woman’s rapid weight gain won’t win in a court of law. But it sure is suggestive.

And GI problems are growing in our society. Not just celiac disease, but irritable bowel looksmore common. Plus we know next to nothing about how gut bacteria change the brain – and vice versa.

We will – in time. Once we view the body as a living, breathing information system whose complexity makes the flow of information on the Internet look like a game of checkers.

In the meantime people need to remain careful and skeptical. The fecal transplant centers recently set up throughout the world will have to prove they effectively treat ulcerative colitis and Crohns – which they’re getting a lot of money to do. Patients who get fecal transplants will have to be followed for decades to find out what actually happens to them.

Most importantly, people will have to see themselves as a vast ecosystem whose non-human inhabitants influence very personal decisions – like what they want to eat and when. Then – if we’re lucky – we might notice we’re part of a much larger ecosystem, in which our eating, socializing, driving and entertainment habits affect millions of other species – on which our survival depends.

We’re all in this together, folks. Obesity isn’t just up about diet and exercise. Thousands of species inside and outside us have a say. And they don’t have to register to vote.