Undereating and Its Effects on Gut Health and the Microbiome
The beginning of the year is when all the latest diet fads along with restrictive mindsets are in full bloom. Often these advertised over-promising diets have components of restrictive and under-eating. Undereating and gut health go hand in hand but what comes first the chicken or the egg is often overlooked. Your gut is unhappy with what you eat so you eat less overall to avoid the misery or your undereating is a cause of your gut issues. Whichever one it is, the fix isn’t as simple as “just eat more” as we know there are SO MANY factors that go into our complex relationship with food!
Undereating is defined as taking in fewer calories (along with vitamins and minerals) than the body needs to maintain proper function. One may or may not be intentionally undereating and there are many reasons why. The implications for undereating may lead to dysregulation in both physical and mental functioning which goes well beyond just hangry. Symptoms may range from subtle to not-so-subtle including fatigue, frequent illness, changes to hair, skin, and/or nails, changes in mental health, fertility, and constipation, to name a few.
Impacts on Hormone Signaling:
Despite perceived stress as low, a reduced caloric intake or undereating produces a physiological stress response in the body even when perceived stress is low. In response to this stressor, cortisol is released.
Cortisol can affect gut transit time, alter gut bacteria, increase intestinal permeability, and alter nutrient availability through the gut-brain axis, a bi-directional communication pathway between the gut and the nervous system. There are pretty clear links between stress and IBS and IBD. There are many more hormone-signaling pathways in the body, outside of the gut, affected by the stress of undereating but we will not go into them here. Because I work mainly with IBS clients, addressing stress- whether psychological or physiological is something that all clients work on as a foundational piece to their gut health.
The Gut-Microbiome Connection:
The gut microbiome is made up of over a trillion microorganisms (which will be referred to as bugs or bacteria in the remainder of this post to simplify) that reside in the gastrointestinal tract, with the majority residing in the large intestine. Gut bugs are involved in many other important processes that extend beyond the gut, including metabolism, body weight, and immune regulation, as well as brain functions and mood.
We can think of our microbiome as a garden with a diverse variety of crops. Certain crops prefer certain fertilizers (which essentially provide nutrients to the soil to grow the crops) so we need to have a variety on hand. When we choose to eat the same foods over and over and lack variety in our diet we may lose a few crops along the way. When we are undereating we further reduce the availability of nutrients and fertilizer to our garden and our crops may lose not only variety but may also not be able to grow very well and our garden will be pretty sparse.
Microbiome Alterations:
For example, a pretty well-known species that is a hot topic in the gut health and functional medicine space is the Akkermansia muciniphila species. This species in the gut helps produce a healthy mucosal lining and is fueled by dietary polyphenols, or plant compounds which are found mainly in fruits and vegetables.
A quick side note on polyphenols: there are over 8000 species of identified compounds. Some common ones you may have heard of include epigallocatechin gallate (EGCG) in green tea and resveratrol in grapes. They have many health benefits including cardio-protective, anti-aging, anti-cancer, anti-diabetic, and neuro-protective to name a few!
Consuming red polyphenols can fuel the Akkermansia species which in turn produces a healthy mucosal lining. If we aren’t eating these polyphenol-rich foods or the fertilizer source for Akkermansia then this species would be low and our mucosal lining in the GI tract may not be as robust as it should be. This is just an example of one species that is affected. Imagine the trillions of other gut bacteria that may be impacted in a similar way.
Impacts on Gut Function:
As a result of undereating with altered hormone signaling and alterations to the gut microbiome, the gut becomes a dysbiotic state. Referring back to the garden analogy, dysbiosis is when we have a decrease in the variety and growth of healthy crops and may start to see more weeds in the garden and sometimes those weeds can also overgrow.
Additionally, with lower overall intake from a restrictive diet, we may find ourselves constipated (we’ll address this larger topic in a later post). Whether this is a result of under-eating or a result of alterations in gut bacteria is the question. One reason for this could be SIBO which you can read about in a previous post. With a lower intake of nutrients, we may be missing those key nutrients to make stomach acid, which plays a key role in kicking off the digestive process. To learn more about nutrients and the key roles of stomach acid hop back to this blog post. If you want to dive in further, here’s a quick video from the University of Michigan that breaks down the digestion process and all the organs and fluids involved.
Summary:
Again we may find that food in general or certain foods make our guts feel unwell, which leads to undereating to feel better, but that in turn exacerbates these issues and the cycle continues. Or perhaps we decided to try a diet as a way to try and control weight, but it may have impacted our gut and we are now dealing with gut dysfunction. The result of undereating has impacts on our overall hormone signaling pathways which leads to alterations in our gut microbiome which in turn has impacts on our mental health and mood, metabolic health, and immune health. WOW that was a LOT to follow!
Start Your Path to Healing:
One thing you can do to get started is to look back to the start of your digestive troubles and create a timeline of what was happening around that time. For example, was there a high-stress period, a change in health/diagnosis, IBS, a mental health challenge, a change in your relationship to food, or was it at the start of a new diet? Starting to put those pieces together is a great first step in this journey.
While there are many reasons one may have arrived here, there is no one-size-fits-all answer. While this is not an easy or quick process, it will in the end bring more reward than being caught in the same repeating cycles and patterns without resolution of gastrointestinal symptoms.
In this new year, I encourage you to shut off the noise of restrictive practices with the promises of quick fixes. Like a swimmer in a race, stay focused in your lane because if you look at what everyone else is doing that can cause some serious unrest in your lane. If that means a social media break until the dust of the new year diet culture settles or shifting accounts you follow to be more food-inclusive, then do it because your nervous system is worth it. While you dial down the “noise” of restrictive fad diets, consider investing your time in things that bring you peace and joy and when you feel ready, you can connect with my services here.
References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10197139/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9220293/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2835915/
https://eating-disorders.org.uk/information/the-effects-of-under-eating/
