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The human microbiome is made up of trillions of bacteria, but are largely made up of two basic bacterial phyla, Firmicutes and Bacteroidetes. Many of you may have had your microbiome evaluated and were told you are doomed to weight gain because you have too many Firmicutes. But… not so fast!
Many articles suggest that the more Firmicutes that populate your gut, the more prone to obesity you might be. If you are lucky enough to have a gut that is populated with predominately Bacteroidetes, you have a better chance of being thin. Your obesity risk and ability to lose weight is supposedly predetermined by your Firmicutes/Bacteroidetes ratio.
Some studies show that one’s Firmicutes/Bacteroidetes ratio is determined in utero, suggesting that there is nothing you can do about your weight if you have the wrong bugs. While this is true to some extent, others studies suggest that the microbiome can changes dramatically with diet and lifestyle. (1,2)
While the majority of studies agree that a predominance of Firmicutes is linked to weight gain, there are plenty of studies that have found just the opposite. So, before you throw in the weight loss towel and resign yourself to your stable of the wrong, fat-storing bacteria, let’s look at the facts.
First, we cannot forget about the overwhelming amount of science that has linked poor dietary and lifestyle choices like eating fatty and sugary food, over-eating, excessive stress, lack of exercise, hormonal imbalances and side effects of some drugs that have been linked to obesity risk. (1)
With regards to the Bacteroidetes and Firmicutes, it seems the research is still out and there may be overruling factors, such as stress, that could cause Firmicutes to store fat and Bacteroidetes to burn it.
The bacteria that populate the gut consume indigestible carbs (resistant starches) and proteins (such as gluten), and through a process of fermentation, convert them into health-promoting short chain fatty acids (SCFAs) along with some gasses.
Firmicutes Deliver Health Benefits
Firmicutes, which have been linked to obesity risk, are surprisingly in charge of some amazing health-promoting and weight-balancing bodily functions. Firmicutes produce the lion’s share of butyrate, which is one on the gut’s most important SCFAs. Butyrate serves as the primary energy source for colonic epithelium. It has been found to increase insulin sensitivity by improving mitochondrial function and stimulating beneficial gut hormones in animal studies. (1) The presence of butyrate-producing microbes has also been linked to healthy weight via their ability to enhance intestinal barrier function. (3) It has been shown to give protection against diet-induced weight gain by stimulating the synthesis of satiety hormones that tell the body to stop eating. (1)
Doesn’t it seem strange that the Firmicutes are responsible for all these weight loss processes and yet still linked to a life sentence of weight gain?
Note: I have written about how ghee is the highest dietary source of butyric acid and, thus, supports a healthier microbiome.
To make this even more confusing, there are genomic studies showing no significant link between Firmicutes and weight gain. In one study, they did not find any difference in the proportions of Bacteroidetes and Firmicutes in the feces of lean versus overweight subjects. In another investigation, overweight subjects even had a ratio of Bacteroidetes to Firmicutes in favor of Bacteroidetes, and many authors have shown no change or even an increase of Bacteroidetes in overweight individuals. (1,2)
What We Know About Bacteroidetes
Bacteroidetes are primarily responsible for the production of two other SCFAs called acetate and propionate. Propionate is a SCFA that is absorbed through the portal circulation taking this fatty acid back to the liver, where it participates in gluconeogenesis, the process by which the liver converts stored fat into glucose to maintain healthy blood sugar levels. (1) Propionate may also be involved in weight maintenance functions like favorable leptin expression, reduced intake of food and reduced cholesterol synthesis. (1) Acetate is involved in cholesterol synthesis and the synthesis of lipids in the liver – processes linked to weight gain in human and animal studies. (1)
While many studies suggest that a higher population of Bacteroidetes is linked to healthy weight and weight loss, a major driver of healthy weight loss is butyrate, of which 90 percent is manufactured by Firmicutes. The science is no doubt confusing, but studies also show that stress, diet, lifestyle and pre- and probiotics have been shown to alter the ratios of Firmicutes and Bacteroidetes.
Bottom line: Do not believe the articles in the media that tell you that you are doomed if your gut is populated with Firmicutes. To support the gut and its important SCFA production, consider the following:
- Avoid processed foods.
- Eat beans/legumes (well-cooked) twice a day.
- Avoid sugar.
- Reduce red meat consumption to 10% of your diet.
- De-stress with meditation – your bugs love this!
- Re-populate your gut with pre- and probiotics. >>> Learn about my 4-Steps to A Healthy Microbiome Probiotic Plan.