Gut Bacteria

Body Fat Is Linked to Gut Bacteria, Not a Sluggish Metabolism

by Mike Mutzel


The obesity epidemic is hard to ignore. The media regularly features stories about some aspect of our national weight-control problem and the American Medical Association recently classified obesity as a disease. One is considered overweight when their BMI is between 25 and 30. About 68 percent of Americans aged twenty and older fall into either the overweight or obese camp because they weigh more than is ideal for optimal health.

All this extra fat is having a huge impact on our health. Today, 30 percent of fifty-year-olds and more than 60 percent of those over sixty-five have at least one chronic disease.

 …since the 1980s, there has been an almost 300 percent increase in chronic conditions in children

The maxim that you gain weight when the amount of calories you eat exceeds the amount you burn is generally accepted as fact. But that formula is not the whole story of obesity.

Researchers have discovered, for instance, that when our fat stores are overfilled, our other systems, especially the immune system, go awry. Eventually fat loss becomes even more difficult, which is one reason why overweight people tend to become obese and why obese people get even fatter.

Photo From: Int. J. Environ. Res. Public Health 2015, 12(1), 162-175
Photo From: Int. J. Environ. Res. Public Health 2015, 12(1), 162-175

You’re Not Fat Because You Have a Sluggish Metabolism

The myth that one can have a sluggish metabolism has been disproven. Researchers from Finland tracked obese and lean twin pairs and found that while the obese twins’ activity level was low, they had higher total energy expenditure and a higher resting or basal metabolic rate (BMR) compared to the lean twins. This study also revealed that while the obese twins had a faster resting metabolic rate than the lean twins, the obese twins had an impaired ability to burn fat. So it seems that in general, overweight people have problems burning fat.

How Gut Bacteria Are Involved in Fat Burning

New research has demonstrated that bacteria in your intestines play a huge role in fat burning; and our metabolism in general.

Through a somewhat complicated mechanism, our gut microflora inhibits normal production of a protein called fasting-induced adipose factor (FIAF). This protein’s job is to block the transfer of fat from circulating cholesterol particles into adipocytes and muscle. When FIAF is inhibited, more fat gets packed away in fat cells than normal.

It’s also been suggested that bacterial imbalances created by high-fat feeding further suppress FIAF and increase fat deposits. Even more interesting are studies showing that berberine, one of my favorite fat-fighting polyphenols, increases FIAF and curtails fat deposition in adipose tissue and muscle. For weight loss and blood sugar improvements, I suggest 900 to 1500 mg of berberine HCl each day with a meal.

Short Chain Fatty Acids Made by Gut Bacteria Impact Fat Cell Synthesis

“Short-chain fatty acids (SCFA) epitomize the notion that when we eat, our microbes are eating too. The bacteria in our gut ferment our food, synthesizing three main types of SCFA—acetate, propionate, and butyrate—in roughly a 70:20:10 ratio.167 The ratio and amount of SCFA produced is contingent upon the type of microbes in the intestine as well as the type of foods eaten.

A recent study compared levels of SCFA and fecal microbiota between European children and children who live in a rural African village and eat a diet rich in plant fibers with no processed carbohydrates. Among the many differences between these groups, it was observed that children of rural Africa have increased levels of gut microbes, including Bacteroides and Faecalibacterium, which are known to produce healthy SCFA.

These children had nearly double the amount of these anti-inflammatory SCFA in their intestines and in a more balanced ratio among the different fatty acids compared to European children. European children had increased acetate-to-propionate ratio; acetate being a main substrate to synthesize cholesterol and other lipids.

Studies in humans suggest that overweight and obese people have an imbalance of SCFA, possibly too much propionate, which is involved in forming fat cells. This may be due to the high saturated-fat content of the diet, which skews the gut microflora balance. Research does suggest that such a diet reduces the number of bacteria in the gut, while decreasing production of healthy SCFA.

In contrast, studies suggest that propionate and butyrate may offer protection against obesity by increasing gut satiety hormones and reducing inflammation.

Summary and Key Takeaways

Imbalanced gut microbes affect body composition, inflammation, and metabolism in many different ways. The dysbiosis (gut bacteria imbalances) weakens your intestinal barrier and increases the burden of inflammatory molecules. Imbalanced gut microbes also increase the levels of unfavorable secondary metabolites, such as short-chain fatty acids (SCFA) and volatile organic compounds which affect fat cell synthesis and fat metabolism.

Healthy digestion and diets of colorful, high-fiber vegetables, fruits, herbs and spices, such as curcumin, and resveratrol have been shown to favor the proliferation of healthy, fat-fighting gut microbes.

A diet rich in fermented foods and prebiotic compounds from inulin in foods such as onions, leeks, and root vegetables are highly protective because they act like fertilizer for intestinal microflora.


Belly Fat Effect: The Real Secret About How Your Diet, Intestinal Health, and Gut Bacteria Help You Burn Fat

Sanchez, M., Panahi, S., & Tremblay, A. (2015). Childhood Obesity: A Role for Gut Microbiota? International Journal of Environmental Research and Public Health, 12(1), 162–175. doi:10.3390/ijerph120100162


Join the conversation

  1. "Studies in humans suggest that overweight and obese people have an imbalance of SCFA, possibly too much propionate, which is involved in forming fat cells. This may be due to the high saturated-fat content of the diet, which skews the gut microflora balance. Research does suggest that such a diet reduces the number of bacteria in the gut, while decreasing production of healthy SCFA"

    Is this implying that you recommend a diet low in all saturated fats ( including grass fed meats, coconut, etc.)? And that saturated fat is indeed one of the key components to being overweight?

    Just curious since that has been a big topic in the whole foods diet conversation.

    Thanks for the article!:)

  2. How do I recover from SIBO, low lactobacillus ("not growing" per Genova CDSA 2200), +1 yeast, low butyrate? I was eating diet 40-60% fats (some saturated from meat protein, some full fat Greek yogurt, coconut/oil, some omega3s (my omega profile is good per Boston Heart Labs, but I'm also oxidizing). Am giving up ALL sugar now including fruit and molds/yeast, and sat fats? I have a SNP which showed that I should be low-fat, but I can't remember which one. This makes sense for me as I try to lose another 60 lbs. I'm left with meat and veg and hoping it's very temporary as I deal with SIBO and try to create biosis. 🙂 Will butyrate and lactobacillus change once I get rid of SIBO – I guess that's my question.

  3. HI Mike:

    Not sure if you have come across this info yet, but thought it might be of interest:

    – Article from the Kavli Foundation:

    Could gut microbes help us treat brain disorders?

    Mounting research tightens their connection with the brain


    Rob Lamberton

    Functional Medicine Consultant

    The trillions of microbes that inhabit the human body, collectively called the microbiome, are estimated to weigh two to six pounds—up to twice the weight of the average human brain. Most of them live in the gut and intestines, where they help us to digest food, synthesize vitamins and ward off infection. But recent research on the microbiome has shown that its influence extends far beyond the gut, all the way to the brain.

    Over the past 10 years, studies have linked the gut microbiome to a range of complex behaviors, such as mood and emotion, and appetite and satiety. Not only does the gut microbiome appear to help maintain brain function but it may also influence the risk of psychiatric and neurological disorders, including anxiety, depression and autism.

    Three researchers at the forefront of this emerging field recently discussed the microbiome-brain connection with The Kavli Foundation.

    “The big question right now is how the microbiome exerts its effects on the brain,” said Christopher Lowry, Associate Professor of Integrative Physiology at the University of Colorado, Boulder. Lowry is studying whether beneficial microbes can be used to treat or prevent stress-related psychiatric conditions, including anxiety and depression.

    One surprising way in which the microbiome influences the brain is during development. Tracy Bale, Professor of Neuroscience at the School of Veterinary Medicine at the University of Pennsylvania, and her team have found that the microbiome in mice is sensitive to stress and that stress-induced changes to a mother’s microbiome are passed on to her baby and alter the way her baby’s brain develops.

    “There are key developmental windows when the brain is more vulnerable because it’s setting itself up to respond to the world around it,” said Bale, who has done pioneering research into the effects of maternal stress on the brain. “So, if mom’s microbial ecosystem changes—due to infection, stress or diet, for example—her newborn’s gut microbiome will change too, and that can have a lifetime effect.”

    Sarkis Mazmanian, Louis & Nelly Soux Professor of Microbiology at the California Institute of Technology, is exploring the link between gut bacteria, gastrointestinal disease and autism, a neurodevelopmental disorder. He has discovered that the gut microbiome communicates with the brain via molecules that are produced by gut bacteria and then enter the bloodstream. These metabolites are powerful enough to change the behavior of mice.

    “We’ve shown, for example, that a metabolite produced by gut bacteria is sufficient to cause behavioral abnormalities associated with autism and with anxiety when it is injected into otherwise healthy mice,” said Mazmanian.

    The work of these three researchers raises the possibility that brain disorders, including anxiety, depression and autism, may be treated through the gut, which is a much easier target for drug delivery than the brain. But there is still much more research to be done to understand the gut-microbiome-brain connection, they said.

    Mazmanian’s lab is also exploring whether the microbiome plays a role in neurodegenerative diseases such as Alzheimer’s and Parkinson’s.

    “There are flash bulbs going off in the dark, suggesting that very complex neurodegenerative disorders may be linked to the microbiome. But once again this is very speculative. These seminal findings, the flash bulbs, are only just beginning to illuminate our vision of the gut-microbiome-brain connection,” said Mazmanian.

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