Gut microbes may be associated with obesity

What role do gut bacteria play?

    • Our bodies need bacteria. When you consider the human Inner Ecosystem you’ll find loads of bacteria in different places of our body.
    • Bacteria are needed in our intestines for multiple reasons.
    • Gut bacteria synthesize essential vitamins and amino acids which help break down food and increases nutrient absorption.
    • During the past decade, there has been some research suggesting that gut bacteria may affect our bodies in several different ways.
    • It is thought that these bacteria produce hormones, neurotransmitters, and inflammation that can then enter our circulation.
    • One study showed that when the bacterial flora from obese mice was transferred into lean, healthy mice, the thin mice gained weight as well.
    • Other studies took gut bacteria from thin mice and placed them into obese mice, the obese mice had better insulin resistance which is a factor in weight gain.
    • There are two common types of bacteria in our gut, Bacteroidetes, and Firmicutes.
    • Obese humans tend to have more Firmicutes.
    • When obese people went on a diet and lost weight, the proportion of Bacteroidetes increased.

Can gut bacteria affect how many calories we absorb?

  • Yes, bacteria can help break down food which then allows increased calorie absorption.
  • Simple sugars are easily dissolved whereas complex sugars known as polysaccharides are not.
  • Bacteria produce enzymes that help break down the polysaccharides to simple sugar which are then absorbed.
  • It is unclear what comes first, the weight gain or the change of gut bacteria.
  • Reference JAMA. 2017;317(4):355-356. doi:10.1001/jama.2016.20099

Processed foods and gut bacteria

A diet high in processed foods are associated with less diverse bacteria colonies.

An article from Scientific American stated,

“A diet of highly processed foods, for example, has been linked to a less diverse gut community in people. Gordon’s team demonstrated the complex interaction among food, microbes and body weight by feeding their humanized mice a specially prepared unhealthy chow that was high in fat and low in fruits, vegetables and fiber (as opposed to the usual high-fiber, low-fat mouse kibble).”

Fecal transplantation, diabetes, and change in weight

  • The worldwide prevalence of obesity and type 2 diabetes mellitus (T2DM) continues to rise.
  • There is a potential role of the gut bacteria in these metabolic disorders.
  • Obesity is associated with changes in gut bacteria.
  • Diabetics have lower numbers of diverse bacteria in their gut.
  • In this study, fecal matter with gut bacteria was transferred from one human to another.
  • Lean males bacteria and stool were transferred to another make who had obesity and diabetes.
  • The male who was obese showed an increase in the number of different types of bacteria in their gut and an improvement in insulin resistance.
  • It is unknown how gut bacteria /fecal transplant appears to improve insulin resistance.
  • There are several theories.
  • The bacteria may produce byproducts such as butyrate which help improve metabolic conditions.
  • Reference Diabetes Care. 2015 Jan;38(1):159-65. doi: Insights into the role of the microbiome in obesity and type 2 diabetes. Hartstra AV1, Bouter KE1, Bäckhed F2, Nieuwdorp M3.

Gut microbe association with obesity and diabetes

  • “Type 2 diabetes mellitus (T2DM) and obesity represent two of the biggest global health challenges of this century and are associated with significant comorbidities and health care costs.”
  • “Research over the last decade has demonstrated that the microbes that colonize the human gut may play key contributory roles.”
  • “Gut microbes contribute to human health through roles in polysaccharide breakdown, nutrient absorption, inflammatory responses, gut permeability, and bile acid modification.”
  • Numerous studies have suggested that disruptions in the relative proportions of gut microbial populations may contribute to weight gain and insulin resistance.
  • Reference Role of the Gut Microbiome in Obesity and Diabetes Mellitus Gillian M. Barlow, PhD, Allen Yu, BS, Ruchi Mathur, MD Nutrition in Clinical Practice  Vol 30, Issue 6, pp. 787 – 797


gut bacteria and obesityGut bacteria and inflammation

  • Gut bacteria communicate in ways that are poorly understood
  • Cardiovascular disease, diabetes, mental illness, asthma, obesity, the metabolic syndrome, and inflammatory bowel disease may be associated with gut bacteria as they can increase inflammation. 
  • “The ultimate goal is to be able to use this information to improve health.”
  • Reference Up To Date



Gut bacteria short chain fatty acid production and obesity

  • The role of short-chain fatty acids production in obesity is uncertain. 
  • “microbiota produces a wide range of metabolites, including short-chain fatty acids (SCFA). “
  • “Many biological effects seem to be mediated by these bacterial metabolites but a conclusive proof is not available for many of the health claims made for SCFA.”
  • “Promising in vitro and animal studies have been published but they cannot be easily extrapolated to the human situation.”
  • There is concern that the production of short chains fatty acids may increase the risk for weight gain and diabetes.
  • Front Microbiol. 2016; 7: 185. Published online 2016 Feb 17. doi:  10.3389/fmicb.2016.00185 PMCID: PMC4756104 Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health David Ríos-Covián, Patricia Ruas-Madiedo, Abelardo Margolles, Miguel Gueimonde, Clara G. de los Reyes-Gavilán, and Nuria Salazar*

Probiotics have been shown to help with antibiotic-induced diarrhea as the gut bacteria change when oral antibiotics are administered.

It is evident that more research is needed but there is hope that additional research may lead to an understanding of weight gain, obesity, and diabetes as well as future treatments.

What role do you think gut bacteria plays?


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