Gut Bacteria and Weight: Everything You Need to Know

Have you tried all the conventional weight loss remedies? Like counting calories, minding macros, portion controlling, low-fat low-carb, high-fat no-carbs, maybe even keto and still the weight stayed? Or perhaps it worked for awhile but now that weight has crept back on and you’re back to square one?

You are not alone. 

Weight concerns are a global problem. Meaning you’re in good (and ample) company if this is you, with nearly two thirds of the world population who qualify as obese or even just over-weight!

That’s nearly 2 billion people…

It’s not just you.

There is something else going on.

And while these numbers are frightening, it means that your weight is not all your fault. 

  • It’s far bigger than calories in calories out.
  • It’s much larger than a lack of willpower.
  • And it’s certainly more serious than a few extra kilos around the middle. 

Every year, obesity is responsible for millions of premature deaths – 4.7 million worldwide!

It really is a global epidemic. 

And until how we hadn’t really figured out how to tackle it with long term results.

What Weight is Healthy?

But before we get too far into it…let’s take a closer look at what a healthy weight looks like.

Now from the outset, I’d like to say that EVERYONE’S ideal weight is different.

There are just so many factors:

  • Heritage – genetics, stature and inherited tendencies …
  • Lifestyle – stress, work, family …
  • Location – food availability, climate …
  • Culture – social habits around food and body shape …

And so many more!

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Which might leave you wondering…

How can we possibly compare weight globally with so many unique variations?

It’s a very good question and something that will need close revision if the global trends continue as they are.

The method we use currently is called the Body Mass Index.

You’ve likely heard about it referred to as BMI. It’s a system which attempts to create a similarity index. And then provides thresholds or limits for a healthy weight range.

How Weight is Compared

This is how weight statistics are generated. Using BMI.

The calculation looks like this…

Screenshot 2020 10 14 at 14.59.56

And you get a number that relates to your BMI.

bmi chart
BMI Chart created by

It’s certainly not perfect – for example BMI doesn’t account for muscle mass being heavier than fat…

  • Elite athletes: Many heavyweight athletes or bodybuilders find themselves classified as obese. Despite a very low body fat composition – all due to their higher than normal levels of lean body tissue.
  • Asian heritage: People of Asian background are smaller in stature and have a lower healthy weight BMI range.
  • Polynesian origin: These people tend to have a higher healthy BMI range.
  • Older people: Our elderly often have a higher healthy BMI range too.
  • Pregnancy: The range is not applicable here as weight gain during pregnancy is often necessary for a healthy baby and should be temporary.

So it’s important to remember that the BMI equation is only a guide. And is only for adults and should not be used for children.

The currently accepted ranges are shown below
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I’m sharing this with the intention of helping you understand two important points:

  1. BMI comparisons are not perfect (there is new evidence to support just that)
  2. BMI is how current weight statistics are generated (we are going to see a lot of them shortly)

Please keep all this in mind when contemplating your own weight situation. A healthy diet and lifestyle is far more important than weight. We all have a healthy normal. And it’s never exactly the same as someone else’s.

As always it’s best to consult a qualified health practitioner if you have concerns. Or just want to talk it all through.

Now we’ve cleared that up, let’s have a closer look at what all the weight fuss is about.

How BIG a problem is weight loss?

Two generations ago, our grandparents typically didn’t have weight concerns. The population wasn’t overweight.
In fact it was rare to know someone who was.

Contrast that to now with these numbers from the World Health Organisation (WHO)…
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That’s an increase in 400 million people in 8 years!

Or in different terms, the WHO reports that worldwide obesity has tripled since 1975.

So what’s changed…?

In short … EVERYTHING.

And that ‘EVERYTHING’ even has a name. 

The “Obesogenic Environment” …

This term has been coined to describe the multiple factors at play driving obesity.

…Meaning we have collectively created the perfect environment for obesity to thrive.

A global state of dis-ease that promotes humans to store fat.


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Weight Gain Layers of Complexity

By indirectly creating the perfect obesity storm…

  1. Diet – High-fat, high-sugar & nutrient deficient ‘easy & processed’ food habits. Intaking far more energy than we use.
  2. Inactivity – Low physical activity. For example, prolonged TV habits are highly predictive of obesity and diabetes.
  3. Stress – Mental health and psychological conditions like depression play an important role in weight retention.
  4. Sleep reduction – Not getting adequate or regular sleep has been linked to weight gain. Keeping a regular sleep or circadian rhythm is so important.
  5. Genetics – Both your maternal and paternal genetics play a role in your likelihood of being obese. But they are only part of the story.
  6. Birth – Changes to the way we enter the world have a direct and devastating effect on our health. And promote obesity as adults.
  7. Toxin exposure – “Obesogens” are described as chemicals that disrupt our hormones that regulate metabolism and weight. Like thyroid hormone and estrogen.
  8. Food supply – Everything from agricultural practices, food processing, marketing, distribution and transportation has changed. All have a role in the quality of our food.
  9. Social pressures – Obesity promoting activities and traditions have quickly claimed their place in our modern culture. Alcohol consumption is a big one.
  10. Microbiome changes – Significant changes to our microbiome affecting the diversity and balance of our gut bacteria can encourage weight gain. Antibiotics and antibacterial chemicals and the Western Diet are key culprits.

Our modern lives are geared to cause weight gain.

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And despite the widely marketed weight loss ‘solutions’….like:

  • Pharmaceutical drugs
  • Surgeries
  • New and better diet advice…and
  • Evermore strenuous exercise regimes

We still can’t lose weight. And if we do – it’s not sustainable long term.

Diseases Connected with Obesity

Which is fuelling the plague of obesity related diseases our world now faces.

While debilitating in their own right these diseases also promote disability, reduced productivity and decreased lifespan.

And for the first time in history our children are also obese.

The rate of obese infants and young children (aged 0 to 5 years) has increased globally from 32 million in 1990 to 41 million in 2016!

Diseases once thought to only affect adults, are starting in childhood.

  • Insulin resistance and precursors for lifelong disease are showing up earlier and earlier.
  • Metabolic Syndrome is now presenting in children and adolescents. Metabolic Syndrome is associated with increased risk of several diseases, like heart disease and diabetes and reduced lifespan.

Clearly obesity is no longer a matter of choice or willpower.

So what is the missing piece? How can we tackle weight – for the long term?

The Microbiome

Recent advances in DNA technology have allowed in-depth research into the links between obesity and our gut bacteria. 

Studies examining the gut microbiome of obese and non-obese individuals are finding distinct differences. Differences that dictate HOW the body (and microbiome) uses energy from the food we consume.

Which all means that our gut bacteria can control the amount of energy released from our food. 

And then how that energy is processed in our bodies!

This shifts how we look at weight concerns. To a dis-ease state rather than just the result of bad food choices.

To understand how our gut bacteria and weight are connected, let’s take a closer look…

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What’s in Your Gut?

Our gut houses a hidden population of trillions of microorganisms. There are said to be between 500 and 1000 species of bacteria living in the human gut – although everyone is different. 

These bacteria use the food we eat to grow and form complex networks. Exchanging nutrients and energy. Both with us and the countless other fungi and viruses that make up our microbiome.

They extract nutrients from our food and release others as part of their own life cycles. Which are then used by our cells to nourish and support our health.

We are a walking ecosystem!

Many factors determine who is living in your gut:

  • We inherit some of our microbiome from our mother’s microbiome
  • Our diet plays a huge role – the food we eat feeds specific groups of bacteria
  • Lifestyle (environment, exercise, stress, relationships) changes our microbiome to a degree far more than we previously thought
  • And of course chemicals, pharmaceutical drugs and antibiotic use have a significant (often detrimental) effect on our gut inhabitants.

In short, our gut bacteria are highly involved with the quality (and quantity) of nutrients taken from our food. Making our gut microbiome the missing link between our current understanding of obesity and what we once thought.

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Our microbes can help our weight (or not).

Microbes can also affect our metabolic processes and influence our gut lining. For example the bacteria called Akkermansia. In addition to it’s leaky gut healing reputation, a healthy gut presence of Akkermansia mucophilia has been associated with better weight loss outcomes.

Others, like E.coli even release proteins that activate that “full feeling”.

In a similar way, particular compounds made by bacteria, like Short-Chain Fatty Acids – SCFAs, like butyrate and propionate actually stimulate gut hormones that reduce food intake.

SCFAs are important in gut health. They are by-products of bacterial fermentation of carbohydrates, like fibre and resistant starch.

They are highly supportive of gut health in many ways and are produced primarily by 2 gut bacteria groups, Firmicutes and Bacteroidetes.

Microbiome Insights to Weight Loss

There has been a significant amount of microbiome research around weight and the ratio of Firmicutes and Bacteroidetes present in our gut.

While there are many conflicting conclusions, it’s generally thought that a higher Firmicutes percentage compared to Bacteroidetes implies you have more energy harvesting bacteria than you may need.

And this can contribute to weight gain. It also points to other diseases.

Let’s take a brief look at each of these groups.

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Firmicutes is a name given to a diverse group of bacteria with similar rod-shaped Gram-positive (stain purple in the lab) physical structures.

The Firmicutes include more than 270 sub-groups each with multiple bacterial species.

Firmicutes are found in various environments and the group also contains some harmful bacteria. They have been shown to be active in fibre and carbohydrate digestion . And many are beneficial SCFA producers.

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Bacteroidetes are another large grouping of bacteria, these are also rod-shaped but Gram-negative (stain pink in the lab). They are well distributed in the environment in soil, sediments and sea water but also in the human gut and animals too.

Bacteroidetes have been found to contribute to a number of functions in the gut including: 

  • Energy production and conversion
  • Amino acid transport and metabolism
  • Carbohydrate digestion

There are many conditions and symptoms associated with dysbiosis or overgrowth between these groups. Everything from IBS to weight control. Far too many to mention here.

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But one interesting point is that both groups produce different SCFAs.

Firmicutes generally produce acetate and propionate – you can see some of the benefits of propionate in the table below.
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And Bacteroidetes produce acetate and the mighty butyrate  – which have important benefits for those managing their weight.

If you are interested in maintaining a balance between these important groups is best approached with the help of Gut Microbiome Testing.

You can check out our program…..

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The Inflammation Connection

Another really important point to understand is the role of inflammation in weight gain. 

Inflammation on the outside might look like a swollen ankle or inflamed rash. Internally inflammation affects the cellular process we rely on for health and causes (and is the result of) many health problems. 

One microbiome cause of inflammation is an abundance of ‘non-beneficial’ bacteria. Many of the ‘bad’ bacteria bring with them immune triggering proteins called lipopolysaccharides (LPS). LPS are part of the cell wall structure of some Gram-negative bacteria. This LPS triggers the immune system and promotes inflammation.

Inflammation also encourages insulin production. Resulting in your body making excess amounts of insulin. And long term overproduction of insulin makes it difficult for the body to burn fat.

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And just as you may have guessed, inflammation and insulin resistance are key players in metabolic syndrome or pre-diabetes.

So now we know the gut microbiome can influence our ability to harvest energy, store or release weight and reduce inflammation – what can we do about it all?

Feeding Your Microbiome

We harness the power and new found knowledge of the microbiome and how it affects our ability to lose weight!

There are many positive steps you can take to control your weight outside of the traditional diet and exercise advice. But one very powerful microbiome-based approach is to eat to promote bacteria that produce those beneficial SCFAs we just talked about.

For example, if you want to encourage butyrate production and Bacteroidetes eat foods that contain resistant starch. For propionate production and Firmicutes – eat legumes, grains, fruits and vegetables.

Good Fats Feed Good Bacteria

Another important factor to consider is the effect fat has on your microbiome. It’s a little more complex than this, but basically, good fats feed ‘good’ bacteria.

And bad fats feed non-beneficial, or ‘bad’ bacteria.

What are bad fats?

Bad fats are those which are processed – like vegetable oils or hydrogenated fats like margarine. 

These fats go through a process called hydrogenation which creates trans fats – these franken fat molecules have chemical structures that are structurally different than our natural fat molecules.

Did you know that every cell in your body needs fat to create its membrane?

These fats are high in omega-6, naturally occurring fats have a healthy balance between omega-3 and omega-6. Too much omega-6 has been shown promotes inflammation and weight gain. 

They are created in high-temperature, high-pressure chemical driven processes. Not at all natural. 

It’s best to avoid processed oils like canola, soybean, vegetable and other seed oils where you can.

Not only do they promote cellular inflammation and irregularities – they also encourage the growth of ‘bad’ bacteria, they contribute to heart disease, diabetes, cancer and depression.

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What fat should we use?

Sources of good fats (and omega-3) include grass-fed beef, wild-caught fish and some plant oils like extra-virgin olive and coconut oils and of course avocados.

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The Western Diet Effect

Although inflammation gets a lot of attention in obesity and disease, one of the biggest contributors to weight issues is the Western Diet and lifestyle.

What do I mean by that? A diet full of processed fatty food and sugar accompanied by a lifestyle that does not support gut health.


  • Takeaway Food – commonly made with cheap, unhealthy oils
  • Processed or Packaged Foods – lacking fibre and full of sugar and damaged fats
  • Chronic Stress – a strong inflammation promoter creating a ripple effect in an already unbalanced microbiome.
  • Antibiotics and Chemicals – the overuse of antibiotics, drugs and other environmental toxins wrecks havoc on our gut bacteria – both good and bad.
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Putting It All Together!

So now that you have a good idea of what helps and hinders weight and health. Let’s look at 6 ways you can promote healthy weight. And nourish your microbiome while you are at it!

1. Eat Whole Foods
Whole foods are naturally higher in fibre, they are not processed and feed the bacteria you want more of. 

Focus on leafy greens (they are rich in fibre) and keep your blood sugar levels balanced. A good rule of thumb is to make ⅔ of your plate vegetables – combine this with healthy fats and good protein sources. 

And you’ll be well on your way to better gut health.

2. Eat More Resistant Starch
Resistant starches like cassava, green bananas, cooked and cooled rice are all great sources of this wonderful microbiome food. 

Resistant starches can’t be digested by us and rely on bacteria to break them down. When they do we reap the benefits of the wonderful bacterial by-products – like the SCFAs we talked about earlier.

3. Get Your Healthy Fats

Remember omega-3s contribute to a healthy microbiome. 

Get your fill of avocados, olive oil and grass-fed butter. Avoid the franken vegetable fats we discussed – it’s easier than you think. If you simply choose to avoid processed foods, you’re most of the way there. 

Check pantry and fridge items like mayonnaise, dressings, dips and spreads – they are often hiding in these foods. They are also easy to make at home – check out our recipes for inspiration! 

You could even take a high quality fish oil to ensure you are getting enough healthy omega-3s.

4. Try Fermented Foods

Fibre-rich foods like vegetables and fruit are prebiotics, meaning they are food for good bacteria. 

Another way to promote good bacteria is to eat them, while they are eating those prebiotic fibres – like in fermented foods. They directly innoculate your gut with beneficial bacteria that help to discourage the bad. Excellent options are sauerkraut, kimchi, miso and kefir. 

You can make these at home too!

5. Find a Good Probiotic

Another great way to get beneficial bacteria is with probiotic supplements. 

High-quality probiotics have a higher number of CFUs (colony forming units) per capsule and more diverse strains. With my clients I recommend quality, well studied, practitioner brands with specific strains to suit the individual.

6. Sleep Well

The last one here is to make sure you get enough sleep. This can be difficult when working long hours and managing a family but being well-rested is essential if you want a healthy microbiome.

Studies have shown that sleep deprivation can result in weight-gain, altered gut bacteria and lowered insulin sensitivity. Effects can be seen in as little as two nights of poor sleep!

So make sure you get the recommended  7-8 hours of quality sleep. For the sake of your microbiome (and your weight).

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The Bottom Line

To lose weight or prevent it creeping on you need a balanced and flourishing microbiome. You need to feed it the foods that encourage your beneficial bacteria. And limit those that don’t.

You don’t need to try all the latest diets and supplements out there today – just follow the 6 basic steps we’ve covered today to revitalise your gut.

If you are keen to get started but feel like you need a little extra guidance, our Gut Heal & Nourish Program may be just what you are looking for.

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