Don’t rely on calorie-controlled diets – they just don’t work.

In a new book by Professor Tim Spector, a leading genetics expert at King’s College London – there’s a compelling evidence, about the truth of the above statement.


Furthermore, he’s offering a tantalising new theory regarding what actually makes us fat — which could revolutionise our approach to weight loss.

Professor Spector is leading a worldwide research into the trillions of bacteria living in our stomachs; he thinks they control our health and moods in many ways – and that the food we’re eating nowadays are having a negative effect on them.

The professor has since two decades been scientifically following 11,000 identical twins, looking into information on their health, lifestyles and diet habits to determine the role of environmental and genetic factors in disease.


One of his findings is contrary to the general view that the cause of current obesity epidemic is people taking in more calories, and burning fewer through exercise, than previous generations did.

Professor Spector explains that if two identical twins are put on high-calorie diets, where they eat an extra 1,000 calories every day — six weeks later they’ll report different changes in weight. Some will have gained as much as 13 kg, others as little as 4 kg — all on identical diets.


It’s a clear evidence that calories aren’t the sole factor. So what’s going on? Professor Spector thinks the main factor is the bacteria in our gut. He says his research findings have confirmed that type and variety of our gut bugs have an astonishing influence on many aspects of our health.

‘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.’

He says his research has found links of our gut microbes to our cardiovascular health, risk of diabetes and mental wellbeing. In his book, The Diet Myth: The Real Science Behind What We Eat, Professor Spector contends that through accurate diet regimen and regular exercise, we can adapt our personal mix of gut bacteria to become one that keeps us happy, healthy — and lean.

Furthermore, he believes that bacteria is the likely culprit behind our obesity epidemic. He thinks the root cause is: ‘our modern diet’ and its effect on our gut bugs. The kind of diversity of microbial species living in our guts is pittance when we compare it with our ancestors.

1500 years ago man used to eat nearly 150 ingredients in a week. Presently, we eat fewer than 20 separate food items, and many — if not most — of these are artificially refined, says Professor Spector.

He was helped by his 22-year-old son, Tom, when he set out to determine what a modern-day junk food diet does to our gut bacteria. For ten days Tom, a student took only Chicken McNuggets and Big Macs, and washed them down with McFlurry ice cream desserts and regular Cokes.

On the sixth day he felt bloated and sluggish. On the eighth day, he’d begun to sweat after the meals. ‘Tom found that his [university] assignments took even longer than usual,’ says Professor Spector. ‘Friends remarked that his skin seemed to have a yellow tinge and he looked unwell.’

In those ten days Tom gained 4 lb. The results of the tests on his gut bacteria, were even more shocking — in just three days 40 per cent of the bugs in his gut had died.

Bad bacteria thrive on a junk food diet

The results showed that Tom’s levels of firmicutes, which create chemicals that fuel our cells with sugars, fatty acids, proteins and vitamins, enabling the body’s myriad systems to communicate with one other properly — had halved.


Meanwhile, the bacteria linked with inflammation had multiplied; these bacteria cause cancer, heart disease, and damage to the immune system.


Professor Spector’s research on twins has revealed many significant findings in relation to bacteria. Notable differences were found in gut microbes of four pairs of twins – where one was obese and the other was not. The leaner twin in each pair ‘had a richer and healthier set, and the fatter twin had a less diverse, inflammatory-looking profile’.

Stool samples were then taken from the twins and transplanted into the guts of mice. ‘The results were surprisingly clear-cut,’ says Professor Spector. ‘The mice receiving the fat twins’ stool samples quickly became 16 per cent fatter.
‘This was clear proof that fat-associated microbes are really toxic and can be transmitted like an infection. The toxic microbes are more likely to grow rapidly in our guts and be a problem if other microbes are suppressed or if there is a lack of diversity.’

Naturally slim? Thank your gut!

Professor Spector carried out test on a microbe called Christensenella, which is associated with being lean. When his team transplanted it into mice, it prevented them getting fat — despite their being on high-fat diets.


While this works well on lab mice, in humans the answer is bit complicated. Other factors make matters more complicated, like the mix of bugs already in individual people’s stomachs (the mice’s guts were germ-free before the experiments), and the question of whether a person’s individual genes are friendly to Christensenella.

‘Some humans who have this microbe appear to be protected against obesity but, unfortunately, many do not,’ says Professor Spector, who not long ago formed the e British Gut Project, which aims to identify the ‘bacterial diversity’ of the British gut and how it affects our health.


Professor Spector says his twin studies prove beyond doubt that modifying our gut bugs offers a surer and safer way of staying lean than going on calorie-controlled diets.

Be good to your gut — do more exercise

Doing just exercise will not cause weight loss, argues Professor Spector. Research also shows it won’t help keep it off. But it will certainly help your gut bacteria. The studies the professor carried out on 3,000 twins show that the amount of exercise they took is the strongest factor in promoting the richness of their gut microbes.


His findings are corroborated by a study of elite athletes in the national Irish rugby squad, published last year in the journal Gut. Nutritionists at University College Cork discovered that the athletes had much more diverse stomach bacteria than normal, as well as lower levels of inflammation.

Artificial sweeteners should be avoided

In the research rats were fed artificial sweeteners at the recommended human doses for three months – the results showed that their levels of bacteria and diversity dropped significantly.

And this specifically harmed the health-enhancing microbes, as per a 2008 study in the Journal of Toxicology and Environmental Health.

The tests on mice showed that artificial sweeteners can alter the balance of gut bacteria, so that the bugs, in turn, release chemicals that, ironically, raise blood sugar levels, increasing the risk of weight gain and diabetes.

But chocolate’s fine… as long as it’s dark

Some study participants at the University of Reading were told to eat cocoa extracts for four weeks — the results showed that their levels of beneficial stomach bacteria had risen significantly. At the same time, levels of potentially harmful bugs and bodily inflammation fell, The American Journal of Clinical Nutrition reported in 2011.


The test suggests that microbes enjoy chocolate as much as we do. In the gut, these microbes help turn chemicals from cocoa into substances that lower the level of potentially harmful fat and ‘bad’ LDL cholesterol in our bloodstream.

So in order to get the benefits without piling on the pounds, go for darker chocolate.