This is why you’re fat…  and it’s not from over eating


In the last few years scientists around the world have begun to discover the remarkable truth about why so many of us are getting fat..  

..and it’s not why we thought

There was much talk some years ago about our genes making us fat. For some people this even became an excuse. It was something I heard a lot – “it’s not my fault, it’s my genes – I was born that way”.  

“it’s not my fault, it’s my genes
I was born that way”

Well for the most part it was an excuse. While there are some interesting discoveries linked to our genes – including some linked to body weight, catually 99.9% of our DNA is identical to our neighbour whether they’re fat or thin.

However looking back at this now – there is some truth to it, only it’s not your genes making you fat, but the genes and make up of the bacteria and microbes that live inside you.

How to restore your gut health
Each of us is home to huge numbers of bacteria and micro organisms that live mainly in our intestines. Counter to popular perception only a small number of these are bad for us – most are harmless and some are actually very important. These strains of ‘good’ microbes help us digest our food, fight infections and generally keep us healthy. In fact they’ve evolved with us and shaped us – without them we wouldn’t exist.

Although we’ve known about the existence of the microbes in our gut for some time, scientists haven’t paid them much attention until recently.

Its only in the last fifteen years that scientists have started to investigate these bacteria and microbes properly and discover some remarkable secrets about them. How they influence our health, and disease, our weight, even our mood and mental health are shaped by them.  

This emerging field of research is hugely complex, challenging some of the greatest minds to piece together exactly how this is happening – but essentially it is changes to the make up of microbes inside us that is making so many of us fat, and ill

Ever wondered why some people never put on weight?

Ever wondered why some people don't get fat?Maybe you have a friend – or colleague – who eats the same diet as you or worse – and never puts on an inch of fat?

My sister is one of these people. She eats everything she shouldn’t. She snacks constantly between meals. Her diet consists of cake, more cake, sweets, doughnuts, fries, burgers, soft drinks – basically anything bad.

..And yet she has never put on an inch of fat, unlike me.  

Well people like her are now considered to be of a lucky few blessed with a particular make up of gut bacteria and microbes that keeps her slim.

Unlike the rest of us – for us it’s a daily battle to keep the fat and the weight off

So if gut bacteria is making us fat, can we get rid of them?

Not really – we need them – or at least we need most of them. Even some of the ones that make us fat help us in other ways. Many of these microbes – a combination of bacteria, viruses, fungi and other organisms – have been with us since birth and the vast majority of them are beneficial. There are hundreds of different strains and they all behave in slightly different ways – but collectively they do us a lot of good:

  • They digest food for us – producing vitamins and nutrients for the body
  • They educate our immune system – helping our white blood cells fight infection
  • They fight off some invaders themselves – preventing pathogens from colonizing
  • And they also influence our brain and our metabolism – affecting our mood and our weight

However this all depends on having the right mix of species – kind of like a rainforest. When there are too many of the wrong species growing out of hand then everything starts to go wrong.. And this is because they also affect

  • How much energy we extract from our food
  • How much energy we burn
  • How much fat we store
  • How hungry we are and the types of foods we crave

So why do we have these ‘bad’ microbes?

Well there are a few possible causes – some aren’t your fault.

You may be able to blame some of this on the microbes you inherited from your mother – or the way you were born and fed and your upbringing – or if you were treated with antibiotics in early childhood – all of these factors are thought to play a role

Then there are other factors which you have more influence over – such as your lifestyle; how much you exercise, how mush sleep your getting, how much stress you’re under, your environment, even your friends (surprisingly we tend to inherit and share some of our microbes with our friends and family!)

and last of all your diet..  and here’s why

It’s the food you eat – not the calories that count

Ok calories count a bit – but not as much as you think.. it’s the type of foods that matter

It’s the food you eat - not the calories that count

It’s the food you eat – not the calories that count

Hopefully you know about the foods you shouldn’t eat – all the fun stuff, the fast foods, takeaways, pizzas, ice creams etc – but you still indulge (and so do I) – they are guilty pleasures that we often crave. We also have cravings for all sorts of packaged foods – from crisps and snacks, chicken nuggets, soft drinks and even ready-meals.

Well what you may not know is that these cravings are no accident – they are driven by certain strains of your gut bacteria – strains linked with obesity and diabetes – that influence your brain telling you to eat more. (They are also driven by addictive stimulants added to these foods which you can learn more about here)

So how can these ‘bad’ microbes make you fat?

All the wrong types of bacteria thrive on the sugar and saturated fat found in your favourite junk foods – and so when you consume a lot of this food – or pretty much anything packaged or processed for that matter – these types of bacteria and microbes thrive and multiply – and then the cravings get louder, the more you eat these foods and the more you feed them.. A vicious cycle!

In the meantime all the really good bacteria that live off fibre and plant matter are getting less of the food they need and getting crowded out by the bad guys, upsetting the delicate balance of species in your gut.

Why is this bad?

Researchers have found that when the wrong types of bacteria take over – your body starts to extract more energy from your food, and store more energy as fat.
In clinical studies the microbiota in obese people were found to increase the amount of energy extracted from their diet when compared to lean people consuming the same diet.

When scientists examine the bacteria in fat people and thin people they can see this difference in gut bacteria with over 90% accuracy.

How to tell if you have bad gut bacteria? 

Take our gut health assessment to find out how healthy is your gutIf you are in good health with a bit of belly fat – then you probably don’t need to worry too much – you can easily improve your gut bacteria by making tweaks to your diet and lifestyle.
However if you are significantly over weight, you get colds or illnesses often or suffer from allergies, food intolerance or digestive problems such as bloating, gas, cramps and diarrhoea – then it is highly likely that your gut bacteria are in an unhealthy state.

Well there are a number of companies and projects that will profile your gut bacteria and give you an indication of how healthy it is – although this analysis is still quite experimental.  Are you curious about your gut bacteria?  Take our gut health quiz to find out if you should be more concerned.

So can you change your gut bacteria to become thin?

Yes – although its not as simple as just taking probiotics alone – and we are not quite there yet with gut bacteria transplants..

The best way to improve the make up of your gut bacteria is to make changes to your lifestyle and your diet – for example a lack of sleep and stress have been found to be as harmful as a bad diet. Exercise also plays a significant role in improving the make up of your gut bacteria.

Meanwhile if your immune system is suffering, be careful – a single course of antibiotics can wipe out vast numbers of our gut bacteria – another factor that can set our delicate ecosystem off balance.  

It takes some effort and it’s not as simple as a quick fix..  if you revert to your old ways, the bad microbes quickly return and so will the weight.

To learn more about these gut bugs and how they can help you shed the weight, read our guide to restoring healthy gut flora

Still keen for more? read our list of ‘healthy’ foods that are surprisingly bad for you and your gut bacteria.


About Author

John Cairn [BA] is a writer and food blogger, originally from the UK with a passion for food, travel and warm climates.