The Appetite Dot

Yesterday we reviewed some characteristics of leptin, a hormone associated with satiety. We also looked at the “hunger hormone” ghrelin. When the brain and the digestive organs communicate about appetite, these chemicals and many more are involved, and the gut microbiome also intervenes. The general theme of this group of posts is the notion of “connecting the dots” which will reveal the effect the intestinal fauna have on our obesity or lack thereof.

Speaking of leptin, here is an example. A study is titled, “The gut microbiota reduces leptin sensitivity and the expression of the obesity-suppressing neuropeptides proglucagon (Gcg) and brain-derived neurotrophic factor (Bdnf) in the central nervous system.” It suggests that our inner bacteria have the ability to thwart what our bodies attempt to do.

How? According to the study:

[T]he gut microbiota reduces the expression of 2 genes coding for body fat-suppressing neuropeptides… Moreover, the presence of body fat-inducing gut microbiota is associated with hypothalamic signs of Socs-3-mediated leptin resistance, which may be linked to failed compensatory body fat reduction.

The bugs can mess with our genes. They can set up resistance to an old-fashioned, basic hormone like leptin. They are tagged as body fat-inducing microbiota, which is the same as calling them obesity villains. These are serious charges!

And they are not the only critters at play in our innards. Clinical nutritionist Mike Mutzel notes that “We have parasites, viruses, and things that we really cannot quantify as readily as we can the bacteria at this point.” He goes on to say:

If you have imbalances in these bacteria, they can extract more energy from the food that you eat. And that energy can form or trigger the body to undergo adipogenesis or the formation of new fat cells. It can inhibit lipolysis or the release of stored fat.

It seems that the microbiota can really sabotage us in a big way. Clues are scattered everywhere, but no one is quite sure, yet, how they fit together or what they all add up to. For instance, this single sentence, from a study titled “Gut-brain axis: how the microbiome influences anxiety and depression,” is fraught with implication:

New studies show that bacteria, including commensal, probiotic, and pathogenic bacteria, in the gastrointestinal (GI) tract can activate neural pathways and central nervous system (CNS) signaling systems.

Our tiny residents do not just sit around, sopping up our leftover nutrients and byproducts. They do things, all the time, without our knowledge, that affect us in more ways than we have begun to realize.

For instance, the mitochondria that provide our cells with energy used to be bacteria, hitchhiking a ride in us (just like the gut fauna do now). Then, around a billion years ago, they became part of us. But their homies, the gut fauna, help them out in various ways, like switching them on and facilitating their reproduction.

The microbiome has a lot of chutzpah, taking over like this. Mutzel says:

Everything you put in your mouth, your thoughts, how you think, how you feel, how you sleep, whether you are grateful or you are mad at the world, all these different things impact the composition of these bugs.

And it goes even further. Quite possibly, everything is reciprocal and the bugs influence our decisions about what to eat, and our sleep patterns, and moods, and attitudes. In the words of the philosopher Voltaire, “The fate of a nation has often depended upon the good or bad digestion of a prime minister.”

These quotations are also apt:

“Unquiet meals make ill digestions.” — William Shakespeare

“Happiness for me is largely a matter of digestion.” — Lin Yutang

“Happiness: a good bank account, a good cook, and a good digestion.” — Jean-Jacques Rousseau

Your responses and feedback are welcome!

Source: “The gut microbiota reduces leptin sensitivity and the expression of the obesity-suppressing neuropeptides proglucagon (Gcg) and brain-derived neurotrophic factor (Bdnf) in the central nervous system,”, 2013
Source: “Episode 31 with Mike Mutzel,”, 2014
Source: “Gut-brain axis: how the microbiome influences anxiety and depression,”, 2013
Photo credit: pilllpat (agence eureka) via BY-SA

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OVERWEIGHT: What Kids Say explores the obesity problem from the often-overlooked perspective of children struggling with being overweight.

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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