According to the analysis of obesity and overweight data conducted by Institute for Health Metrics and Evaluation (HME) at University of Washington, the UK has the third highest rate of excess weight in Western Europe behind Iceland and Malta, at 62%. The USA fairs worse at 66%.

For years we have focused on the many possible causes of weight gain – from excess saturated fats and refined sugars in the diet, combined with a sedentary lifestyle, compounded by health issues that affect our metabolism and hormones. Whilst these factors are all valid and need to be considered in the mix, there’s another factor that has come to light as a major contributor to this sad state of affairs – the gut microbiome.


The microbiome

Each of us has trillions of gut bacteria, weighing up to 2kg, lurking in our bowels. This mass of bacteria could be said to make up an extra organ called the microbiome. Everyone has their own unique microbiome depending on the bacteria they inherited from their mother and even the people they came into contact with after their birth.  Throughout a lifetime, the influences of travel, diet, immunity, all have an impact on the constituents of the gut, both good and bad bacteria.

Gut bacteria and weightloss

Who would have thought there could be such a tangled web within each one of us that not only determines our digestion and immunity, but also our ability to maintain a healthy weight?

So how can we specifically influence our gut microbiome to help our weight loss efforts?

Professor Tim Spector, who is Head of the Department of Twin Research and Genetic Epidemiology at St Thomas’ Hospital, London, has a new hypothesis about why we are gaining weight and why it’s proving so difficult to lose; it’s not as simple as calories in and calories expended, he believes it’s down to the bacteria in our gut! We have only a fraction of the diversity of gut bacteria compared with our ancestors. This is due to the fact that we are only consuming 20 separate food items, and most of the food commonly eaten nowadays is artificially refined.

Modern diet:

‘Microbes are not only essential to how we digest food’, he says ‘they also control the calories we absorb and provide vital enzymes and vitamins, as well as keeping our immune system healthy’. It’s our modern processed diet that has affected the gut microbiome, allowing bad bacteria to proliferate and take over. This can also make us prone to yeast infections and when yeast is present, the effects of sugar cravings are accentuated.

Professor Spector’s son carried out an experiment for his university dissertation where he ate only McDonalds Big Macs washed down with McFlurry ice cream and coke for 10 days! The findings were that he gained 4lbs and killed 1,300 of his gut species! Not only did Tom look and feel terrible, but only 3 days in, his gut bacteria had reduced by 40%! The good news is that once a healthy diet was resumed, the good gut bacteria started to flourish again and improved health was restored.

So the question is – is it the junk food and calories contained that lead to weight gain, or is it the effect the junk food has on the gut bacteria?

To prove his hypothesis, Professor Spector carried out research on four pairs of twins, one was obese, the other wasn’t, putting each pair on the same diet for 6 weeks and noting that they had completely different changes in weight at the end of this period. There were also notable differences in the composition of their respective gut bacteria, with the leaner twin having a richer, healthier profile and the fatter twin having a less healthy, inflammatory profile.

Impact of exercise on gut bacteria:

Results from the Professor’s 3,000 studies on twins shows that exercise has a big part to play in the increase of good bacteria. Studies done at University College Cork show that the Irish National Rugby squad have higher bacterial levels than normal.

Who would have thought that the amount of exercise a person takes would determine the particular mix?

Other ways that we can hypothesise that gut bacteria help our metabolism function, is that it enhances digestion and absorption of minerals and vitamins.

There is also a link to mental wellbeing.  We are more likely to have energy and want to exercise if we are in a good mood and feeling healthy and full of vitality!

Does your gut bacteria keep you slim_2

So what foods can we eat to boost our good bacteria?

There are many delicious foods we can add to our diet to give this process a helping hand – we need to consume food sources for the bacteria itself – these are called prebiotics, and these are found naturally, mostly in the form of plant foods, providing about 30g of fibre daily.

Prebiotics are officially defined as ‘non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, which can improve host health’

Examples of prebiotics are:
sauerkraut, Jerusalem artichokes, chicory, onions, miso, tempeh, as well as nuts, seeds, olive oil (80% of its healthy fats reach the colon where they encourage the growth of healthy microbes, lactobacilli and stop infectious microbes from colonising our gut), coffee, lentils, garlic, bananas, leeks and dark chocolate.

Unpasteurised cheese, yoghurt and kefir are loaded with living microbes called probiotics that are able to influence the health of the gut – this may explain the French Paradox that they live longer than the British with their regular intakes of wine and smelly cheeses! Probiotics are also taken in supplement form.

Moreover, a study in the Journal Science 2011, reported that red wine has an additional benefit to health than heart disease by beneficially affecting gut microbes. Similar effects were found with beer, though I wouldn’t recommend this as a license to drink lots of alcohol!

What to avoid to prevent loss of good bacteria

Sugar and artificial sweeteners both alter the levels of gut bacteria. So the first step in correcting the diet would be to address cravings and balance blood sugar by ensuring the right low GL carbohydrates are consumed. Meanwhile increase the prebiotic foods, though this should be done very gradually as some people can get bloated as a result of a quick dietary change.

So with the right diet, the right level of beneficial bacteria and regular exercise, isn’t it fabulous to know that we can find a better way of staying lean than dieting and deprivation?

Read more from WatchFit Expert Kathleen Farren



Vizhub.healthdata.org shows data from Institute for Health Metrics and Evaluation released 5/2014

How obese is the UK? And how does it compare to other countries? The Guardian, May 2014

Do Microbes Make you Fat and The Diet Myth: The Real Science Behind What We Eat, Professor Tim Spector

The British Gut Project: www.britishgut.org. A study by Professor Spector which aims to identify the bacterial diversity of the British gut and how it affects health.

Journal Science 2011

Study in Journal of Dairy Sciences, 2013

Mail Online Health, 12 May 2015


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