To heal your gut, optimal metabolic health is a must.  A recent study found that 12.2% of the US population has optimal metabolic health.  When you consider that this includes all adults over the age of 18, you may be a bit shocked.  Me, not so much.

From my perspective, this number feels about right.  People have an odd level of delusion when it comes to assessing their own health. And I’ve mentioned how I’ve been guilty of this.  But I also see this all the time with people I work with.

Even when it has nothing to do directly with metabolic health.  For example, I’ve had at least half a dozen clients say their sleep is great despite using a C-pap.  The same holds true for all aspects of health.

I think this alarming data creates an ideal teaching moment for understanding the relationship between metabolic health and the gut.  The criteria they used to assess optimal metabolic health is the same criteria we use for identifying metabolic syndrome. 

Those with optimal metabolic health have 0 of the 5 criteria used to assess metabolic syndrome.  These criteria include:

1. Waist circumference >40in for men, >35in for women
2. Blood pressure >120/80mmHg
3. Fasting glucose >100mg/dL, HgA1c >5.7%
4. Triglycerides >150mg/dL
5. HDL-C ≤50mg/dL for men, ≤40mg/dL for women

If you use the more lenient ATP III guidelines, the number of metabolically healthy is still under 20%(19.9%).  Think about that for a minute. If we use the stringent numbers, only 1 person in 8 doesn’t have at least one of these problems.  If  we are lenient, it’s 1 in 5.

Metabolic disease: A roadblock to heal your gut

The worst part is that once people meet 3 of these 5 criteria, their risk for chronic disease increases substantially. Chronic diseases of the gut are no exception.  And it’s impossible to heal your gut if your metabolism is wrecked.

For example, people with metabolic syndrome have twice the risk of IBS than those who don’t.  Another study found that those with metabolic syndrome have an 8.9x higher risk of gallstone disease.

Interestingly enough, it appears that in a lot of cases, gut dysfunction precedes development of the metabolic syndrome.  In other words, gut problems creep up before you meet 3 of the above 5 criteria.  In fact, this appears to be exactly the case with non-alcoholic fatty liver disease(NAFLD), it precedes metabolic syndrome.

In people with mild NAFLD, the risk for metabolic syndrome is 3.6x higher. For those with moderate to severe NAFLD, the risk is 9.4x greater.  We also have data showing that people with high amounts of visceral fat or a larger waist circumference have a a 9.4x and 7.8x greater risk of IBS, respectively.

But when we really dig in to the gut dysfunction that comes with metabolic syndrome, the picture is crystal clear. A broken metabolism makes for a broken gut.

Metabolic syndrome, NAFLD, and the microbiome

Most aspects of the metabolic syndrome associate strongly with NAFLD and microbial dysbiosis.  Most people assume this means that taking prebiotics or probiotics may be useful approaches for metabolic syndrome.  I don’t hold this view. And a recent study on NAFLD and this approach sums up my thoughts on the subject:

“The administration of probiotics and prebiotics as a cure-all remedy for all chronic diseases is not advocated, instead, the incorporation of evidence based probiotic/prebiotic formulations as adjunctive modalities may enhance lifestyle modification management strategies for the amelioration of NAFLD”

Simply put, this means that pre- and probiotics may be useful secondary approaches, but primary care centers around changing lifestyle.  In fact, the only useful therapeutic approach to addressing NAFLD is fat loss.  This is because the liver isn’t making fat out of thin air, it requires excess calories. 

NAFLD and feeding

There is no single initiating factor, NAFLD is a multi-hit problem. It requires excess calories from either sedentary behavior or calorie over-consumption to progress to metabolic syndrome.

We can take a look at the commonalities between NAFLD and gut disord IBS. This gives a pretty clear picture of why they associate so strongly with one another.  In both, we see:

1. Inflammation/immune activation
2. Leaky gut
3. Altered gut motility
4. An impaired gut-brain axis

Thus, I don’t think the microbiome is a good therapeutic target.  The reason is fairly straightforward.  I believe that metabolic changes that lead to NAFLD and metabolic syndrome impair healthy digestion, which alters the microbiome. 

The change in the microbiome alters gut-liver communication, causing disease progression.  This change is driven by lifestyle, and reinforced by the change in the microbiome, not caused by it.

So, in my model, the microbiome is a biomarker that perpetuates disease, not the underlying problem that causes it.  Armed with this knowledge, we can dig deeper to look at how NAFLD and metabolic syndrome change gut function.

You can’t heal your gut with metabolic dysfunction

There are many ways metabolic problems and the lifestyle factors that drive them cause gut dysfunction.  The liver plays a large role in gut function by synthesizing bile acids and secreting factors that regulate intestinal permeability. The gut helps the liver regulate bile synthesis and participates in glucose and triglyceride metabolism.

In fact, one can argue the 2 components of the metabolic syndrome that relate specifically to liver metabolism, elevated blood glucose and triglycerides, are at the very least reinforced by changes in the microbiome.  This is why probiotics and prebiotics seem like a viable option. 

They just don’t work because behavior drives the changes in the microbiome, and behavior is needed to reverse them.  Which is probably why the most effective strategy at reversing NAFLD to date is lifestyle modification. Specifically, centered around dietary restriction, aerobic exercise, and resistance training.

Metabolic dysfunction damages nerves

Another way that metabolic dysfunction impairs gut function is through autonomic nervous system dysfunction.  The autonomic nervous system helps regulate automatic processes including all aspects of digestion.  People with metabolic syndrome with the presence of both impaired glucose regulation and high waist circumference experience autonomic dysfunction.

The reasons for autonomic dysfunction hit on both arms of the autonomic nervous system.  Autonomic nervous system dysfunction may actually begin prior to metabolic syndrome through increased sympathetic nervous system activity. The sympathetic nervous system functions as the “fight or flight” wing of the autonomic nervous system.  A recent review indicates that increased sympathetic nervous system activity likely plays a role in IBS, fibromyalgia, chronic fatigue syndrome, and interstitial cystitis.

Poor glycemic control and nerves

Poor glycemic control and/or insulin resistance can also impair function of the vagus nerve, impairing sensory nerves that assist with timing in the gut as well as motor nerves that regulate gut motility.  The vagus nerve is the conduit through which the brain and gut communicate. It regulates the parasympathetic nervous system, which helps us “rest and digest”.

The bad effects of hyperglycemia are also evident in nerves of the enteric nervous system, the resident nervous system in the gut.  Enteric nerves are also damaged by hyperglycemia which essentially reinforces the same effects as damage to the vagus nerve.  The effects of hyperglycemia on both enteric and the vagal neurons are believed to underlie:

1. Altered GI motility
2. Increased “leaky gut”
3. Delayed gastric emptying(Gastroparesis) in people with Type 1 and Type 2 diabetes

Motility takes a second hit as the Interstitial cells of Cajal, which help regulate motility, are also damaged by hyperglycemia.

Metabolic dysfunction allows the microbiome to encroach

One final way that metabolic syndrome affects gut health may come as a surprise.  In a study performed in 2017, researchers looked at the proximity of bacteria to the cells lining the colon. 

Researchers found that people with poor glucose control had bacteria that were invading the inner mucus layer. This increased increases inflammation by allowing bacteria to interact with the gut wall. People with healthy glucose control did not, even those who were obese.

This doesn’t mean that all people with gut problems have metabolic syndrome.  What it clearly illustrates is that if you do have a metabolic issue, address it first to heal your gut. 

So if you checked off any of the 5 criteria above, you have a target to go after.  Of the criteria required for metabolic syndrome, blood glucose management seems to be incredibly important for fixing the gut.

But you don’t need Type 2 diabetes or metabolic syndrome to experience these problems.  Even a relatively healthy person can experience hyperglycemia under the proper conditions, and these conditions aren’t even remotely rare.  And as we age, the pump is primed to make these conditions more pathological. 

For example, after a woman goes through menopause, fat storage patterns change. This leads to a preference of forming for metabolically damaging visceral fat over subcutaneous fat.

Conclusion

Metabolic syndrome and NAFLD associate with gut disorders for multiple reasons.  For one, the the physiological changes that come with these disorders alter the way the gut functions. 

Additionally, the lifestyle factors that increase the risk for metabolic syndrome and NAFLD impair the gut as well.  The data showing an increased risk of IBS in people with greater waist circumference and visceral fat illustrates this.

It would be incorrect to say that gut disorders are caused by metabolic dysfunction. But I think it’s clear that metabolic dysfunction makes functional gut disorders worse.  Therefore, if your goal is to heal your gut, fixing metabolic health should be an absolute priority.