Our microbiome is made up of hundreds of trillions of organisms; bacteria, fungi, yeasts, viruses and archaea. All of these organisms work together to help us to absorb nutrients from our food, make additional vitamins, support mood and cognition, regulate the immune system and many, many more crucial functions that support our wellbeing.

With so many bacteria, and more bacterial genes than human genes, it goes without saying that our microbiome plays its own role in all health and disease states. With respect to weight gain, research in this area kicked off in the year 2000 when Norwegian scientists transplanted stool from obese mice into thin mice. With no changes to their food or calorie expenditure, the thin mice gained weight quickly.

The main players

There are two main bacterial groups (phyla) in the human gut; Bacteroidetes and Firmicutes. In general terms, the Bacteroidetes phyla are anti-inflammatory, they improve immune function, make essential vitamins that we cannot get in our food (vitamin K and B7 for example), and they help to regulate your metabolism. These are predominantly Lactobacilli and Bifidobacterium genus bacteria, as well as Bacteroides, Roseburia, Bifidobacterium, Fecalibacterium, and Enterobacteria.

The Firmicutes phyla are an important part of the microbiome, too. They prevent infection, support digestion and produce energy as well as other important metabolites. When they’re out of balance or overgrown in comparison to other key bacterial groups, they can impact our metabolism by increasing the production of inflammatory mediators. This leads to increased insulin production, sugar cravings, more gut imbalances and over time –  weight gain, too. 

How does your gut contribute to weight gain?

Several studies have shown that obese patients' microbiota contain higher levels of pro inflammatory species such as Staphylococcus, Enterobacteraceae and E.Coli  and less anti-inflammatory species such as Roseburia, Faecalibacterium and Akkermansia mucniphila than their counterparts of a healthy weight.

These bacteria produce LPS (lipopolysaccharide) which is readily absorbed through the gut wall into the bloodstream. LPS induces the inflammatory response which contributes to insulin resistance and increased fat storage.

Your gut, your hormones and your appetite

Another way the gut influences weight is through hormone signalling. We have a variety of hormones that are produced in the fat cells, gut and liver that tell the brain when to eat and when not to eat. Ghrelin signals hunger, and high Bacteroides and Prevotella activity as well as diets high in processed foods, have been shown to increase ghrelin levels and result in higher food intake.

Other appetite signalling hormones; peptide YY and leptin, signal fullness and reduce food intake. Higher populations of Bifidobacterium, Lactobacillus and Eubacterium result in higher leptin and peptide YY, and therefore lower food intake. Also, certain bacteria have been shown to affect caloric uptake from the diet because they have an increased ability to break down and ferment dietary starches and carbohydrates.

On the flip side, there are specific species that reduce inflammation, restore the gut lining and produce metabolites that reduce hunger, insulin and systemic inflammation. Akkermansia muciniphilia is a key species in this group. People with low Akkermansia populations have a higher incidence of obesity, inflammatory bowel disease, type 2 diabetes and cardiovascular disease. The opposite is the case for people with optimal Akkermansia populations - they have lower blood sugar, lower body weight and less incidence of chronic disease.

What you can do about it?

Now you know how the gut impacts metabolism, you may be wondering how balance can be restored. There is no need to feel discouraged, with lifestyle and dietary change, the microbiome adapts quickly. Research shows that significant change in bacteria populations can occur as quickly as within a few weeks. Here are a few general tips to improve gut function and metabolism;

 

• Eating a high fat and high sugar diet increases inflammation and also increases populations of pro inflammatory bacteria. So, reducing your intake of fast food & highly processed foods will help to reduce populations of bacteria that contribute to metabolic disorders and weight gain. 

• Gut health foods; fibre. A study found that ingestion of oligofructose, a prebiotic fibre that promotes the growth of Bifidobacterium and Lactobacillus, decreased the secretion of ghrelin in overweight humans. This is true of all fibres in wholefoods such as vegetables, fruits, nuts, legumes and wholegrains. Beneficial fibres in supplement form also restore your gut, have a look at the Gut Co’s very own gut-loving fibre -

• Akkermansia and our other wonderful metabolism boosting bugs, love dietary polyphenols. Polyphenols are phytonutrients found in fruits, vegetables, herbs and nuts that have bright colours and strong flavours. They are high in antioxidants and have varied health benefits, including optimising the microbiome. Berries, turmeric, pomegranate, green tea, dark leafy greens and cacao are absolutely on this list. As is Repair, by the Gut. Co.

• Fat loss has been shown to restore the microbiota, too, by changing bacterial populations to increase energy expenditure and reduce insulin production. This may seem like a catch 22 - but by increasing gentle exercise, sleeping well and eating more vegetables, both your body weight and gut will begin to return to an optimal composition.

 

This article is general in nature and not intended to diagnose or treat any medical conditions. Speak to your naturopath, nutritionist or doctor if you’re unsure about which lifestyle and nutrition choices may be right for you.

References

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Gomes AC, Hoffmann C, Mota JF. The human gut microbiota: Metabolism and perspective in obesity. Gut Microbes. 2018 Jul 4;9(4):308-325. doi: 10.1080/19490976.2018.1465157. Epub 2018 May 24. PMID: 29667480; PMCID: PMC6219651.

Hills RD Jr, Pontefract BA, Mishcon HR, Black CA, Sutton SC, Theberge CR. Gut Microbiome: Profound Implications for Diet and Disease. Nutrients. 2019 Jul 16;11(7):1613. doi: 10.3390/nu11071613. PMID: 31315227; PMCID: PMC6682904.

I.G. Macchione, L.R. Lopetuso, G. Ianiro, M. Napoli, G. Gibiino, G. Rizzatti, V. Petito, A. Gasbarrini, F. Scaldaferri Akkermansia muciniphila: key player in metabolic and gastrointestinal disorders Eur Rev Med Pharmacol Sci 2019; 23 (18): 8075-8083 DOI:10.26355/eurrev_201909_19024