Appetite, Its Lack, and the Microbiome

One way we can think of the microbiome is as an organ. According to The Economist,

An organ does not have to have form and shape… The immune system, for example, consists of cells scattered all around the body but it has the salient feature of an organ, namely that it is an organized system of cells.

Childhood Obesity News has been exploring the connections between the microbiome and various other things, and between those various other things and obesity. Many questions remain to be answered, but it appears that the microbiome is able to influence appetite and its delinquent sister, craving.

Difficult as it might be to imagine in the midst of the obesity epidemic, the eating disorder called anorexia nervosa (AN) is still much dreaded. In search of a preventative, Japanese researchers…

[…] studied 25 women with AN and compared their microbiomes to 21 age-matched healthy females. They found that AN patients had a lower amount of total bacteria and specifically, lower amounts of C. coccoides group, C. leptum subgroup, B. fragilis, and Streptococcus.

It has been shown that a lack of eating goes along with a decrease in gut flora diversity and a less-than-optimal microbiome.

Nutritionist and trainer Sean Croxton works on the premise that when a person doesn’t take in enough calories, the leptin levels aren’t right, which results in a craving for carbohydrates. Some of the organisms in us are called fat-inducing microbiota, because they can cause the body to resist leptin.

However, the causation/correlation ratio between various bugs and a multitude of reactions has yet to be determined. One study, published in Psychosomatic Medicine, showed that a patient’s Clostridia population can be rebuilt, if that turns out to be desirable.

It does seem that working with the gut bacteria could put an end to anorexia. AN is particularly challenging and tantalizing to researchers because the majority of anorexia patients also suffer from depression. The Microbiome Institute says,

In terms of the mental health aspect of anorexia and the microbiome, the researchers found a direct association between eating disorder psychopathology and microbiome diversity, with lower diversity corresponding to worse eating disorder psychopathology. The same was true for depression, as the degree of depression was inversely correlated with bacterial diversity.

Your responses and feedback are welcome!

Source: “Me, myself, us,”, 08/18/12
Source: “Microbiome therapies may be an option for treating anorexia nervosa,”, 01/07/16
Source: “The anorexia nervosa gut microbiome differs from healthy controls and is related to mental health,”, 10/13/15
Source: “The Dark Side of Fat Loss with Sean Croxton,”, undated
Photo credit: mind on fire (John Nakamura Remy) via Visualhunt/CC BY-SA

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About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
You can contact Dr. Pretlow at:


Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

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