Consider this thought experiment:

Drop a person in a blender (since it's all hypothetical, go ahead and make it someone you don't like. Feel better? I bet you do!). Then, count all the total number of cells that are produced. Only one in ten of these cells will be human. The other 90%? Those are all microbes. If you look at the total number of genes in your human smoothie (NOT coming soon to a Jamba Juice near you), the numbers are even more skewed: only one in 100 genes are human. The rest are, again, bacterial. The total collection of all of these bacteria living in and on our bodies is known as the microbiome.

The idea isn't to gross out the card-carrying germophobes among us. But let's face it: we're just as much bacterial as we are human. Plenty of these microbes live on our skin, in our lungs and genital tracts. The mother lode of microbes, however, live in our gut. They are crucial to extracting energy from food, and these microbes are extremely sensitive to what we eat. Starving mice for just one day dramatically alters the composition of their gut microbes. Specifically, it decreases a type of bacteria known as Firmicutes. When researchers transplanted Firmicutes into the guts of lean mice, they rapidly gained weight (Crawford et al., 2009)

When it comes to eating disorders, there isn't much talk of microbes. There are the occasional papers from researchers like Sergei Fetissov about potential auto-immune responses in people with eating disorders, and some work on PANS (pediatric auto-immune neuropsychiatric syndrome) and anorexia, but generally, researchers haven't looked at the role of the microbiome in triggering or perpetuating an eating disorder.

Much work has been done in obesity research. Scientists have consistently found that people with a BMI >30 have different gut microbes than people with BMIs in the "normal" range. As well, bariatric surgery also significantly changes gut microbes as people lose weight, making them look more similar to the bacterial profiles seen in "normal weight" individuals. A more recent study in The ISME Journal proposed a microbiome diet: eating foods that would eliminate a type of bacteria called Enterobacter helped a person lose drastic amounts of weight in a short period of time (Fei & Zhao, 2012).

So how are microbes involved in eating disorders? No one really knows. Cindy Bulik has begun a study looking at this relationship, but the results still aren't in. Based on the studies above, it's reasonable to assume that ED behaviors (starving, binge eating, and/or purging) will have a significant effect on a person's microbiota. It still has to be measured, but I would bet a lot of money on it. The question is what do these microbial changes have to do with ED symptoms?

Imbalances in gut microbes in mice and rats have been found to alter patterns of risk-taking and anxious behaviors--something that also happens in people with EDs. They could also, perhaps, explain weight loss seen in anorexia and EDNOS. Maybe the initial restricting triggered a significant change in gut microbes that amplified the effects of malnutrition. Maybe they lacked a group of microbes that produced an important hormone regulating hunger and satiety. No one really knows.

One hint to the potential role of microbes in EDs comes from a study published today in the journal Science (Smith et al., 2013). The scientists studied the relationship between gut microbes and kwashiorkor, a form of severe malnutrition that occurs when a person doesn't eat enough protein. Of the 317 twin pairs from Malawi that the researchers followed for three years, half became significantly malnourished and 7% developed signs of kwashiorkor. Obviously, a lack of protein is crucial to the development of this disease but it's not the only factor as not everyone with a severely protein-deficient diet will develop kwashiorkor. Something else had to be going on.

First, the researchers treated twin pairs discordant for kwashiorkor (that is, one twin had it, whereas the other didn't) with "ready-to-use therapeutic food"- basically peanut butter on steroids. Twins with kwashiorkor had significantly different from nearby twins who (presumably) at pretty close to the same diet. The researchers found significant changes to the gut microbes in the ill children with the use therapeutic food. Discontinuing the therapeutic food caused a regression in the functioning of the gut microbes.

The kicker is this: when the researchers fed mice a standard Malawian diet and inoculated them with microbes from the guts of malnourished children, they rapidly lost weight and also developed kwashiorkor. This happened despite the fact that their diets contained adequate calories. One of the reasons that the researchers believed the therapeutic food is so effective at treating kwashiorkor is that it helped restore normal gut microbes.

To say what effect restoring normal gut flora will have on ED symptoms remains to be seen. Probiotics are a hot item, but much of the research is fairly overblown. There's definitely still potential there, and we need to know more about which populations of people are likely to benefit and which aren't. But it's an interesting idea, and I think we need to know a lot more about the role of the microbiome in the development and perpetuation of EDs.

In closing, a quote from scientist John Rawls in an interview with Scientific American:

“We are in the midst of a revolution of our ability to describe the composition and physiological potential of these bacterial communities...What we can begin to speculate on, though, are the different types of relationships that might be taking place. We know gut microbiota enhance our ability to extract calories from complex carbohydrates, which is clearly a mutually beneficial relationship. But it’s thought that all vertebrates have the capacity to digest and absorb other types of nutrients, such as lipids, proteins and simple carbohydrates, so it’s not readily clear how we could enter into a mutually beneficial relationship with bacteria with regard to those nutrients."

I've seen this headline quite a bit when journalists talk about eating disorders. Being a journalist myself (somewhat), I know the lure of a snappy title. Like the article I managed to write about the new choir director with an eye patch after he was in a motorcycle accident...and I spoke of his "new vision." Yeah. Good going there, Carrie. (Jane...this should make you feel better...AND making it into two blogs this week!) A headline is big, folks. It will make people read your story- or run fleeing.

I'm not saying that all articles titled, "Dying to be Thin" are bad or negative or any of that because I haven't read them all, nor do I think a bad title indicates a bad article. No more than a good title indicates a good article.

What I have issue with is the whole dying to be thin concept in general. When I was severely anorexic, I was dying all right. Not to be thin. Not to be anything. Just...dying. Of starvation. A very slow, miserable way to die. I was not doing this so that I could be thin. That's bullshit. It was a thing to latch onto, a way to explain the inexplicable. Why else would I starve myself? It wouldn't be as mundane as something as a phobia of food.

Or would it?

That's what it was, though. When someone who is scared of flying avoids planes, even a Medevac flight, we don't say that they're "Dying to stay on the ground." No. They're scared of heights/flying/whatever. When I had bad OCD in high school and was terrified of germs and AIDS, I wasn't dying to be clean- even though I almost attempted suicide because I didn't know what was happening and was so miserable.

I never wanted to be thin, really. I liked the idea, and it's intoxicating because most women in our society wants to be thin. I thought if I ate healthy and got rid of my tummy, then I would be happy, then things would be okay. I wanted to have the "perfect" diet and exercise routine. I wanted to feel comfortable.

Lo and behold...it worked. The first five pounds, anyway.

That's the thing with obsessions and compulsions. Your brain gets used to it, like an addict develops tolerance for a drug. Then it takes even more (compulsions, hooch, crack, heroin, you name it) to quell that horrific anxiety. And then, no matter how much you do or how little you eat, it isn't enough. Which is when it happens- the only conceivable thing you can identify as what's happening is that you're dying to be thin.

No!

I was dying to avoid food, to avoid my horrific fears. Of course they didn't make sense. Who in their right mind would be afraid of food? Would call Sweet N Low because they heard there were actually calories in those alluring pink packets and bitch them out for false advertising. Starvation drives you completely, utterly insane.

I might add that while I was at my lowest weight, I also had the top grade in the most advanced chemistry class on campus: physical chemistry (aka p-chem).

So don't tell me I was dying to be thin, because I wasn't. My anorexia wasn't about looks, or fashion or really about anything. Except fear.

Here's a question that's near and dear to my heart: how do you define anorexia? There's the DSM-IV criteria which states the individual has to be less than 85% of ideal body weight, and not be menstruating. There's also the loosely used popular criteria of self-starvation. All of which can be true. So how, then, is someone anorexic versus just being a little muddled about how much to eat?

Luckily for us, scientists have been trying to answer those questions. Part of the problem with diagnosing anorexia is that most sufferers deny the presence of a problem. In my case, I didn't really think I was losing too much weight, or if I was, then it wasn't problematic. This all makes a clinical interview with a sufferer rather convoluted to say the least.

Then there's the next question: less than 85% of ideal body weight. It's clear that there is no one "ideal body weight," even when you control for age and height. Think about it: there's over 6 billion people on this earth, and that everyone who is, say, 5'5" like me should weigh precisely 125 pounds is ludicrous! For the vast majority of human history, there haven't even been scales! Yet the species persists.

(Dieters, take note of the above...)

Lastly, there's the need for amenorrhea. This doesn't work with men (obviously, unless the said male also has a functioning uterus, by which send the lad my way so I can write it up in JAMA and get rich!), as well as with young girls and post-menopausal women. However, there are specific hormonal changes that accompany anorexia (such as a decrease in the T3 thyroid hormone) as a side effect of malnutrition. There are also general decreases in sex hormones. This has been shown in men put on a semi-starvation diet- they have a decrease in sex drive and become completely and utterly obsessed with food. Sound familiar? I could go into the chicken and egg debate here, but that's just too much for one post.

There have been clear indications of the genetic links to both anorexia and bulimia, meaning that there's something more than just social pressures going on. There are also numerous structural brain changes that occur in people with anorexia, no doubt related to the malnutrition caused by the disease.

What would I like to see? Standard scientific tests to determine the bio/neurochemical changes that are hallmarks of malnutrition. A 500 pound woman can starve to death. Maybe it will take longer than someone who weighs 150, but it will happen. And it is the effects of malnutrition that need to be reversed, not necessarily weight gain (as would be the case for the starving 500 pound woman). I have had wonky thyroid levels at a weight higher than my usual. Right now, when I am a little shy of my pre-AN weight, my thyroid levels are within normal limits. Why? I'm giving my body the nutrition it needs. Weight be damned. I would also like to see PET scans used for diagnosis, rather than just research. They're expensive, to be sure, but a good diagnosis is worth its weight in gold.

No diagnosis is that easy. Hopefully, more and more people with anorexia will be diagnosed and treated before the disease becomes severe, which could make blood and brain tests less precise. But until we know more accurately what happens to a person suffering from anorexia, it will be hard to create an adequate case definition.