How Gut Bacteria Influence Your Metabolism
STORY AT-A-GLANCE This article was previously published September 30, 2019, and has been updated with new information.
Before we review the evidence that your gut fiora plays a role in regulating your metabolism and likely is a factor in the development of obesity, please understand that there is beyond overwhelming evidence that excess seed oils and an increase in linoleic
acid is likely the primary factor contributing to the obesity epidemic as discussed in my interview with Tucker Goodrich . Hippocrates once said that "all disease begins in the gut," and the more we learn, the more accurate that statement proves to be. As noted in a 2018 paper:
"While often-quoted figures suggest that the microbes that live in and on thehuman body outnumber human cells by 10:1, a more recent estimate suggeststhat we are essentially one part human to one part microbe in terms of cellnumber.These commensal microorganisms have a vital role in human health. Theybreak down otherwise indigestible dietary fibers and other components of food,produce vitamins, promote the development and maturation of the immunesystem, and prevent pathogenic bacterial species from colonizing the gut."
According to evidence cited in this paper, of the 1,000 or so gut bacteria we know of, any given individual will have around 160 different species of bacteria colonizing their gut. This individual combination is known as your gut microbiome, and can have a tremendous infiuence on health and well-being. The diversity of your gut microbiome begins to be established when you are an infant, and is affected by genetics, whether you are breast- or bottle-fed, and your immediate environment. Later in life your microbiome is significantly affected by your food choices. Diets high in sugar and processed foods may reduce the diversity and your overall health, while diets high in whole foods high in fiber tend to have a beneficial impact. For example, a number of studies have found obese individuals tend to have a less diverse gut microbiome, in addition to having greater numbers of certain harmful bacteria and fewer beneficial ones. Studies have shown obesity is associated with as much as a 40% decrease in diversity, and that improving that diversity through probiotic supplementation can help resolve
123456metabolic defects, resulting in fat loss.
Obesity Associated With Frequent Diarrhea
There's also a link between abnormal bowel movements and obesity, according to research published in September 2019. As reported by Medical Xpress:
"In the most comprehensive analysis of the relationship between Body MassIndex (BMI) and bowel habits to date, published today in AlimentaryPharmacology & Therapeutics, a team of physician-researchers at Beth IsraelDeaconess Medical Center (BIDMC) found a strong association betweenobesity and chronic diarrhea independent of an individual's dietary, lifestyle,psychological factors or medical conditions …'While several previous studies have pointed to an association between obesityand bowel habits, all lacked data on whether dietary or other factors drive theconnection,' said corresponding author Sarah Ballou, Ph.D., a healthpsychologist in the Division of Gastroenterology, Hepatology, and Nutrition atBIDMC.'Our research confirms a positive association between obesity and chronicdiarrhea and reveals for the first time that this relationship is not driven byconfounding factors such as diet or physical activity level.'"
Looking at data from the 2009-2010 National Health and Nutrition Examination Survey, the researchers found 8.5% of obese and 11.5% of severely obese individuals reported chronic diarrhea, compared to 4.5% of those with normal weight. "Stepwise regression revealed that severe obesity was independently associated with increased risk of diarrhea," the authors say. Unfortunately, this study cannot shed light on why this is happening. One hypothesis is that chronic low-grade infiammation is at play. Not only is chronic infiammation a factor in obesity, but it can also contribute to diarrhea.
78910Systemic infiammation is also believed to be one of the leading triggers for other serious diseases, including neurological degeneration, Type 2 diabetes and cardiovascular disease — all of which, by the way, are also associated with obesity. Committing to making changes to your gut microbiome can do far more than improve your bowel habits. Your gut health is important to most aspects of your health, including reducing your risk for cancer, metabolic syndrome and depression.
Probiotics Shown to Alter Metabolism
Improving your microbiome can be as simple as increasing your intake of fermented foods or taking a quality probiotic supplement. Previous research has demonstrated that probiotics — beneficial bacteria found in fermented and cultured foods such as yogurt — have a measurable effect on your metabolism. One such study, published in 2008, found the bacterial strains Lactobacillus paracasei and Lactobacillus rhamnosus affected a number of different metabolic pathways, including the metabolism of: Hepatic lipids Amino-acids Methylamines Short-chain fatty acids (SCFAs) As reported by Science Daily:
"Adding 'friendly' bacteria changed the makeup of the bugs in the gut, not onlybecause this increased the number of such bacteria, but also because the'friendly' bacteria worked with other bacteria in the gut, amplifying their effects.One of the many biochemical changes observed by the researchers was achange in how mice treated with probiotics metabolized bile acids. These acidsare made by the liver and their primary function is to emulsify fats in the upper1112131415
gut. If probiotics can infiuence the way in which bile acids are metabolized, thismeans they could change how much fat the body is able to absorb."
While some claim taking probiotic supplements or eating fermented foods won't have a significant impact on your microbiome, this particular study found otherwise. As noted by corresponding author Jeremy Nicholson with the department of biomolecular medicine at Imperial College:
"Some argue that probiotics can't change your gut microfiora — whilst there areat least a billion bacteria in a pot of yoghurt, there are a hundred trillion in thegut, so you're just whistling in the wind.Our study shows that probiotics can have an effect and they interact with thelocal ecology and talk to other bacteria. We're still trying to understand what thechanges they bring about might mean, in terms of overall health, but we haveestablished that introducing 'friendly' bacteria can change the dynamics of thewhole population of microbes in the gut."
Can Probiotics Effectively Aid in Fighting Obesity?
So, can probiotics actually have a beneficial impact on obesity? A number of studies suggest the answer is yes. Among them is a 2013 animal study, which found the probiotics Lactobacillus gasseri BNR17, found in human breast milk, act as an obesity inhibitor and antidiabetic. According to the authors, "The administration of L. gasseri BNR17 significantly reduced the body weight and white adipose tissue weight regardless of the dose administered." Such findings jibe well with studies showing breastfed babies have a significantly lower risk of childhood obesity. In another study published that same year, obese participants with a fasting blood sugar level above 100 mg/dL were given either BNR17 or a placebo for 12 weeks. At the end of the study, the treatment group had shed more body fat than the controls. As reported by the authors, "Despite there being no change in behavior or diet,
16171819administration of only the supplement of BNR17 reduced weight and waist and hip circumference." Lactobacillus gasseri has also been shown to ease symptoms of irritable bowel syndrome and ulcerative colitis, thanks to its anti-infiammatory effects. L. gasseri is also one of four bacterial strains shown to help eradicate Helicobacter pylori, a primary cause of stomach ulcers. A more recent review, published in the journal Nutrients in February 2019, sought to "present evidence … demonstrating the effects of various probiotic strains and their potential eficacy in improving obesity and associated metabolic dysfunctions." As noted in this paper:
"A large body of evidence has described several possible mechanisms by whichthe gut microbiota can contribute to, and/or infiuence, obesity.Although so much is still unknown and debatable, thus far there is a generalconsensus that the gut microbiota is implicated in obesity through dietarycarbohydrate fermentation, lipogenesis, excess energy storage, and severalother pathways including a vast array of metabolites, hormones andneurotransmitters, some of which are known to control food intake and theregulation of energy balance."
How Gut Bacteria Can Infiuence Your Fat Stores
Three main phyla or groups of gut microbes make up the human microbiome and serve diverse structural, protective and metabolic functions: Bacteroidetes — Porphyromonas, Prevotella and Bacteroides Firmicutes — Ruminococcus, Clostridium, Lactobacillus and Eubacteria Actinobacteria — Bifidobacteria (the most prevalent type)
2021222324As explained in the 2019 Nutrients review, in your gut, these bacteria protect your health by "displacing harmful bacteria, competing with pathogens for nutrients and producing antimicrobial factors." Structural functions provided by them include "developing the immune system, inducing immunoglobulin A (IgA), and reinforcing the mucosal barrier," while metabolic functions "benefit the host by synthesizing vitamin K, folate and biotin" and play a role in the absorption of minerals such as magnesium, calcium and iron. Importantly, gut bacteria also help break down the foods you eat and ferment digestive- resistant starches, turning them into beneficial SCFAs, which help modulate your immune response and infiammation. As explained in the 2019 Nutrients review:
"Degradation of dietary polysaccharides and fiber by Bacteroides andFirmicutes in the gut results in the production of SCFAs, such as propionate,acetate, and butyrate.Propionate is an important energy source for the host via de novo synthesis oflipids and glucose in the liver. Acetate is used in peripheral tissues as asubstrate for cholesterol synthesis while butyrate represents a rich energysource for the epithelial cells that line the colon.Furthermore, microbiota is involved in the control of energy balance, foodintake, and satiety via gut peptide signaling, through hormonal effects in theblood or by modulating the nervous system directly. The appropriate balance ofthese regulatory peptides may be disrupted if the microbiota composition isaltered …SCFAs … also serve as signaling molecules that can activate G-protein coupledreceptors (GPRs), including GPR43 (also known as free fatty acid receptor 2) inadipose and intestinal tissues.In adipose tissue, SCFAs bind to GPR43, thus promoting adipogenesis andincreasing energy expenditure. In intestinal tissue, SCFAs bind to GPR43252627
leading to secretion of anorexigenic peptides … resulting in improved glucosetolerance and increased energy utilization."
Since SCFAs play such an important role in fat accumulation, the two phyla that produce SCFAs, Firmicutes and Bacteroidetes, may be used as markers for obesity. As noted in the 2019 review, obese individuals tend to have higher proportions of Firmicutes and Lactobacillus and lower proportion of Bacteroidetes and Bifidobacterium compared to normal weight individuals. Studies have also linked specific strains to specific health problems. For example, high levels of Bacteroides vulgatus (which is abundant in the human gut) appear strongly associated with infiammation, insulin resistance and altered metabolism. Low levels of certain bacteria in the Firmicutes phylum, including Blautia and Faecalibacterium, have been linked to the accumulation of trunk-fat specifically.
How Probiotics Can Benefit Your Health and Weight
The 2019 Nutrients review also details the mechanisms by which supplementation with probiotics can improve your health and weight. Key areas of infiuence include: Enhancing the integrity of your intestinal epithelial barrier Enhancing the adhesion of bacteria to your intestinal mucosa, thereby facilitating colonization Producing antimicrobial and other health promoting substances Inhibiting pathogenic microbes by competitive exclusion Modulating your immune system While individual strains of bacteria have been linked to specific health effects such as reductions in trunk fat or lowered infiammation, several studies have demonstrated that multi-strain probiotics may be more beneficial than single-strain ones, as they tend to create synergistic effects.
28293031An Easy, Inexpensive Way to Improve Your Gut Microbiome
While probiotic supplements are widely available, few can compete with traditionally fermented foods, in terms of the diversity and sheer number of probiotics. Fermented foods are also your least expensive alternative, as you can easily make them at home. Using a starter culture will speed the process and ensure you'll end up with a consistent, high-quality product. Remember, your diet is one of the easiest, fastest and most effective ways to improve and optimize your microbiome, so the good news is you have a great degree of control over your health destiny.
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