Gut Microbiome and Weight Loss: 3 Ways Your Microbiome Is Making You Fat
When I was a brand-new Functional Medicine doctor, I attended as many seminars and trainings as my budget would allow.
It was at one of these seminars that I had this “ah-ha” moment about how much power our microbiome has over our body fat.
The speaker told us about a study with two groups of mice - one group was obese and the other was lean. The researchers performed fecal transplants on the mice, taking the bacteria from the poop of the obese mice and implanting it into the guts of the lean mice - and guess what happened? The lean mice became obese!
They didn’t change their food type or quantity or anything else about their environment besides their gut microbiome, and yet these otherwise lean mice got fat.
Crazy, huh? Well, what’s even wilder is they did the same thing, but in reverse, and guess what? When the obese mice got the bacteria from the lean mice…they got lean! I know, pretty cool, right?
Studies like this one have been done - with several variations - since that time, including one study where healthy mice could be made obese by transferring gut microbial matter from obese humans. The researchers also found that transferring gut microbial matter from lean humans to the mice prevented the mice from putting on weight!
If this has your wheels turning because you’re struggling to lose fat, no matter how well you eat or how much you exercise, you’re in the right place.
Because I’m going to share 3 ways your microbiome could be making you fat - and more importantly - what you can DO to shift the balance in your favor.
1. An overgrowth of bacteria can cause an overgrowth of your waistline.
Especially if the overpopulation of microbes in the gut starts to sneak into your small intestine. This creates a condition called SIBO - small intestinal bacterial overgrowth - where microbes that are supposed to live in the colon or large intestine begin to migrate into the small intestine. Once there, they start fermenting your food, particularly carbohydrates, creating gas, bloating, fullness, constipation, and other digestive symptoms.
Not only does this make you feel fat, especially around your midline, but it can also cause actual fat gain.
SIBO, or overgrowth of less-than-friendly bacteria and yeasts, can also release compounds called lipopolysaccarides, or LPS, which triggers inflammation and insulin resistance - also known as pre-diabetes. When your body isn’t as responsive to blood sugar shifts because of this gut-bug-induced insulin resistance, your body fat percent goes up!
Here’s where the struggle gets real: you could be eating a relatively healthy diet, but if your microbiome is overgrown or hanging out in the wrong spot, it’s effectively working against you, which makes maintaining a healthy body fat percentage really, really tough.
It also means that even when you do make big changes and start eating a whole-foods, low-sugar, nutrient-dense diet, it can take awhile for your microbiome to shift and adapt to your new normal, meaning that it will take an extra measure of patience and persistence on your part, which is never fun.
2. An unbalanced microbiome causes cravings and "hanger".
It’s probably no surprise that what’s going on in your brain has a lot to do with fat gain. But you might not realize just how much your microbiome controls stress, cravings, and other feelings that make you prone to reaching for the foods and beverages that sabotage your fat loss goals.
Scientists have found that your gut microbes are responsible for producing 90% of your serotonin neurotransmitter - the hormone in your brain that’s often associated with positive mood.
Let’s say that your gut bugs aren’t balanced, and instead of cranking out healthy levels of happy serotonin, they’re making inflammatory cytokines or methane gas.
Well, you’re probably going to feel crabby, depressed, anxious, or brain-foggy. And your brain is going to look for other ways to get that serotonin kick - but from sugar, instead. That’s right, foods that are high in simple sugars and carbs encourage serotonin production, which is why you might crave cookies, pasta, soda, desserts, and other carbohydrate-rich, processed foods when your gut microbes are out of whack. It’s not hard to see how this leads to fat gain, right?
And here’s an added twist. Not only do your gut bugs impact your brain’s production of serotonin, but they can also change the balance of leptin and ghrelin, the chemicals in your body that are in charge of appetite. Leptin is nature’s appetite suppressant, and tells your brain when you’ve had enough to eat.
Well, some gut microbial patterns can reduce leptin sensitivity, which means that you might not get the message when it’s time to put down your fork. That’s right - your microbiome might actually be causing you to feel hungry even when you’re full!
3. Your microbes can make you Estrogen Dominant.
What is Estrogen Dominance? It happens when estrogen is too high relative to progesterone - that’s important, because you don’t have to have high estrogen overall to suffer the symptoms of estrogen dominance. These symptoms include heavy periods, fatigue, endometriosis, and of course fat gain - especially around the midsection and thighs.
How is your gut microbiome involved? Well, in a couple of ways, actually. Your gut microbes not only produce estrogens on their own, they can also tell your body’s cells to produce estrogens.
But the biggest way that I see an out-of-whack microbiome creating estrogen dominance is through the production of something called beta-glucuronidase.
Quick note about estrogen detox - in order for your body to get rid of excess or already-used estrogens, it needs to send them down a 3-part detoxification journey. At each step of on the path, your body chemically “packages up” these estrogen byproducts so that they can be delivered to the colon and flushed out of your system and down the drain in your poop.
Many of us struggle to detox or metabolize hormones like estrogen because of genetic issues or micronutrient deficiencies in steps 1 and 2 of the process, but step 3 is equally important - and that’s where the microbiome can really mess things up.
You see, sometimes an unhealthy microbiome will create too much beta-glucuronidase in your colon, and this compound essentially unwraps the little estrogen package sent to it from the liver while it’s in the gut.
Once the package is unwrapped, it’s more likely to be re-absorbed through the gut wall, back into the bloodstream, where it adds to the body’s overall estrogenic burden and has to be detoxed all over again. It’s like the worst re-gift ever, and it creates all sorts of hormonal issues, including fat gain.
So, now that we understand just how important a healthy microbiome is to losing fat and keeping it off...
Here are some Functional Medicine strategies I use to assess and address microbiome issues.
If you have symptoms of microbiome imbalance like:
- weight gain
- bloating
- constipation or diarrhea
- gas or belching
- reflux or GERD
- feeling full all the time
- food sensitivities
- chronic fatigue
- overall inflammation
I recommend utilizing advanced functional testing to get more data about the root of the issue. There are several awesome comprehensive digestive tests that measure your levels of helpful bacteria and yeasts, screen for unfriendly parasites or overgrowths of opportunistic bugs, and even tell you how much beta-glucuronidase is actively disrupting your estrogen detox.
And investing in a test like this is going to do more for your long-term health than any elimination diet or candida cleanse, I promise you that.
Once you know if you’ve got SIBO, a yeast overgrowth, gut inflammatory markers, or other indicators of microbial problems, you’ll be equipped to co-create a targeted, individualized plan to resolve those issues.
One of the strategies folks find most helpful involves utilizing specific strains of probiotics that promote direct fat-loss activity in the gut and brain.
For example, the very targeted strain called Bifidobacterium lactis B-420 has been shown to help manage appetite by increasing the levels of an appetite-reducing peptide in the gut.
In a 6-month clinical study, those who took a probiotic containing this specific strain showed reduced body fat mass, reduced waist circumference, reduced abdominal fat, and reduced caloric intake compared to those taking a placebo. Pretty impressive for just one targeted bacterial strain, isn’t it?
Another keystone strain that’s been more recently identified is called Akkermansia muciniphila, and greater concentrations of this strain are linked with leaner body weight, lower fat mass, and greater insulin sensitivity.
P.S. you can measure your Akkermansia using the functional testing I mentioned earlier - many of my clients find they have low levels that need support.
And remember beta-glucuronidase - the compound we talked about that messes with estrogen detox and elimination?
Enter it’s counterpart: Calcium D-Glucarate!
This combo of calcium and d-glucaric acid inhibits the “unpackaging" action of beta-glucuronidase! That means it’s easier for your body to get rid of excess estrogen, which helps prevent estrogen dominance, and therefore weight gain. Calcium D-glucarate also helps your body eliminate other toxins, too, which is a nice bonus.
The relationship between your gut microbiome and your weight is a complicated one.
I didn’t even get into how microbe balance can mess with gut integrity, create inflammation, set you up for autoimmune disease, and even mess up your thyroid and metabolism, all of which ALSO can make you fat!
But I hope you have a deeper understanding of how important gut health is to overall health, and how there’s more to the story of body fat than just diet and exercise.
And of course, I wanted to make sure you had some actionable takeaways to get you started down the path to better microbiome balance.
To take the first step, check out the links below.
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