Book Review. The Diet Myth: The Real Science Behind What We Eat by Tim Spector

by The Health Sciences Academy — Get free science updates here.

We thought it’d be fun to review a book and highlight the kinds of things we noticed that perhaps most readers are not aware of.

Before we get started, just bear in mind that this is not a full, exhaustive, comprehensive analysis. Instead, we’d like to share some pointers so when you do read a diet or health book you keep them in mind.

The Diet Myth by Tim Spector

UK Version  |   US Version   |   CA Version

The Author: Tim Spector, Professor of Genetic Epidemiology at King’s College London and Director of the TwinsUK Registry.

The Low-down: 336 pages with a good twist of humour, and 18 pages of references. With improved bacterial analysis, Spector has recently started looking at how gut bacteria affects our body weight and health. From the perspective of the ‘hidden’ world of gut microbiota, this book lists a number of common diet myths and aims to debunk them.

Our review

Every week, it seems that there is a new ‘hot’ diet to follow in order to improve health, build muscle, burn fat, lose weight, or just to feel great. But there are numerous contradictions between these diets and the overall health benefits can be confusing.

So, we were excited at the prospect of a new perspective focused on gut health. Based on the assessment of microbes, Spector tackles some of the trends of our time, including low-fat, low-carb, high-protein, low-calorie, and food-group restriction.

He cleverly combines real scientific studies with ‘anecdotal’ evidence producing easy-to-read narratives, although he doesn’t look at the entire body of evidence (as we do in our Science Reports) and often skips the full argument by cherry-picking only a couple of points.

After a brief introduction based on his own experience untying the myriad of diet information available, Spector begins by explaining the history of microbes and why they have been overlooked in diet studies for so long (mainly because science first focused on disease-inducing bacteria).

Microbes make up a unique individual ‘footprint’ which is largely genetic, but can also be dramatically influenced by diet.

This is the focus of this book. And given we are estimated to have 100 trillion of these microscopic little fellows in our guts alone, the argument he makes is “we are what our microbes eat.”

Microbes have recently been linked with obesity both in animal studies and through gut-profiling in humans (through faecal swabs).

Animal studies in this area use specially bred, microbe-free mice to ensure there is no predisposition from their own microbes. In one study, the mice had gut microbe transplants from identical human twins (one obese and the other lean). Despite dietary duplication for all mice, the mice with the obese-twin microbe transplant quickly gained weight, while the other mice remained lean.

Further studies looking at the microbes of identical twins showed that very high levels of the rare microbe family Christensenellaceae may be protective against obesity. This corresponds with and is explained (in a lot more detail) in our Science Report: Are Your Genes, Gut Microbiome and Weight Connected?

Dedicated to his research

During the five years Spector spent researching this book, he tried many of the diets himself recording the effects on his gut microbes.

From volunteering for colonoscopies to experimenting with fasting, Spector was dedicated to his research.

To assess the effects of saturated fats, he personally undertook the ‘fromage’ experiment to assess the ‘French Paradox’.

“If eating saturated fat is so bad, why do the French, who every day eat much more of it than the AngloSaxons, suffer from less than a third the rate of heart disease of Brits.”

And so, he ate 180 grams of French cheese per day for three days while collecting stool samples to analyse changes in his microbes.

What did he find?

In only one day, Spector saw changes to his gut microbes. In particular he noted big increases in a number of the lactobacilli (referred to as ‘good’ bacteria).

However, once the cheese diet ended and the normal diet was resumed, the gut microbes returned to normal suggesting the changes were reliant on the cheese microbes.

If you are a cheese lover, you might want to avoid the YouTube video in Spector’s reference list showing cheese mites (Acarus siro) forming the rind of a mimolette cheese. The video demonstrates that cheese is living entity full of microbes, and could put you off cheese for a long time!

China under the spotlight

Besides demystifying a few assumptions from the China Study (led by T.C. Campbell in the 70’s), Spector highlights what mainstream science has been telling us for a while: that dietary cholesterol does not raise blood cholesterol unless you have a familial genetic predisposition. Newer egg studies that we unscramble here also confirm this.

Another topical fat discussed in this book is trans fat. Often present in processed foods yet rarely on the label, trans fats receive a lot of media attention.

There’s a reference to (another) rather stomach-churning YouTube video about the making of Spector’s ‘favourite’ trans fat: ‘gutter oil’ – an illegal oil made in China which, as the name suggests, is derived from recycled fat from the gutter.

Whilst illegal in China, it is estimated that 10% of the oil used in China is gutter oil, so this has become a serious public health issue.

His son as a test subject

To investigate the effects of trans fats, Spector and his son, Tom, recreated Morgan Spurlock’s ‘Super Size Me’ experiment.

Given a recent study reported increased risk of colon cancer in Africans when put on a typical American diet for two weeks, we were interested to read more about his ‘Super Size Tom’ experiment.

Tom ate all his meals from McDonalds for ten days, supplementing only with crisps and beer in the evenings.

At the end of the experiment, Tom had gained two kilograms, reported reduced productivity and noticed a grey tinge to his skin.

More importantly, his microbial diversity had been decimated and his friendly bifido bacteria rates halved.

In three days, he had lost 40% of his detectable species! It took over two weeks for Tom’s microbiome to be restored to their previous numbers.

Whilst one man doesn’t make a scientific study (!), this does show the devastating effect that junk food can have on our microbes.

Gene mutations

Throughout the book, Spector emphasises that we all have individual microbes, genes, and process food differently.

Spector gives a couple of nutrigenomics examples, such as the lactase gene mutation that allows most Europeans to digest lactose since about 6,500-12,000 years ago.

Another example of genetic adaptation is the ability to process alcohol.

Spector explains that Asians “carry a variant of the alcohol gene dehydrogenase which metabolises alcohol fifty times faster than in Europeans or Africans, who lack that variant.” Quite why the Asian population carry this variant is still unknown.

Our critique points

There has been a lot of hype about this book in the media, mostly praising the thorough insight into a relatively, unexplored area.

We do have a couple of critiques:

The majority of the population do not know what gut microbes are, or why we should be interested in them, and this should have been explained at a much earlier point in the book. Instead, the microbial explanations are scattered throughout the charters. If this is your first introduction into the dark recess of the gut, a thorough explanation in chapter one would have been helpful.

Although Spector lists many diet trends, when he tries to debunk them he picks only a handful of studies but does not present the entire body of evidence with the depth that we do in our Science Reports.

A reader should be allowed to see both sides of the story and the full picture to make up their own mind, but this book does not accomplish that to our standards. For the novice reader, the somewhat biased arguments can lead them to believe that this is the full story, when it is not.

For example, there are some loose explanations regarding the harm of certain supplements, which miss the context of the cited scientific studies and don’t delve into the detail of why there can be certain side effects – e.g. from dosing, bad combinations, toxicity levels, drug interactions, and all of the other critical factors that we teach in our Advanced Dietary Supplements Advisor course.

Useful takeaways from the book

Your microbes could be largely responsible for you being lean or obese, and these microbes could be influenced both by genetics and diet.

“Many of the smaller subgroups of bacterial families, like lactobacillus and bifidos, found to have major effects on diet, obesity and disease, were also seen to be under genetic influence.”

Variation in the diet is key to gut microbe health. Spector says “no fashionable diet is good for your bacteria unless it contains lots of fibre rich foods.”

If this book, or even review, has you intrigued about your own gut microbes, you can send your own sample for profiling and research purposes by visiting Spector’s

Our verdict

To read or not to read? READ FOR ENTERTAINMENT

Entertainment value: 5/5

Impartiality: 2/5

Context and completeness: 2/5

New discoveries: 2/5

Readability: 4/5

Scientific references: 3/5

Our total score: 3/5

Find this book: UK Version | US Version | CA Version



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  • Deanna Konecny

    Reply Reply August 27, 2015

    Your reviews/summaries are fantastic! I especially enjoyed this book review. I would really like you to review a few books that I’ve learned a lot from and get your stance on –
    1) Wheat Belly by Dr. William Davis
    2) Grain Brain by Dr. David Perlmutter
    3) Brain Maker by Dr. David Perlmutter
    Thanks and keep up the great work!

  • katerina

    Reply Reply August 27, 2015

    I heard a lot about the book Skinny Bitch by Kim Barnouin, do you have any review available for it? i wonder if it is worth it to read it

    • Hi Katerina! I skimmed through Skinny Bitch when it was first released a few years ago and closed it very quickly given the lack of scientific references… It might be entertaining to read though :-)

  • Tina Buchheim

    Reply Reply August 27, 2015

    I have just finished your Nutritional Diploma course and really enjoyed it! I am sure at some stage you referred to Dr Fuhrmann. It would be great to get a review of his book
    “Eat to Live” : )
    Thanks for keeping us entertained in an educational way ; )

    • Huge congrats, Tina! Great to hear you enjoyed your time with us! Science is so much fun, isn’t it :-)

      • Tina Buchheim

        Reply Reply September 1, 2015

        Oh, it so is!! I am not sure I have enough years to learn everything I want to learn!! I might still be a student at 105..! LOL!
        Well, you still have many courses I can work through to start with.. I’m on the Detox course now..

  • Nurten

    Reply Reply August 27, 2015

    Excellent review, Alex. Thank you so much. I do agree with all your comments.
    I have a fairly long time fascination with probiotics ever since I read Dr Gary Huffnagle’s book: “The probiotic revolution”. I read as much as possible whatever comes my way related to this topic, but nothing exceeded so far my appreciation of this particular book. I am pretty much up-to-date with the multitude of the recent studies about probiotics and their multiple roles throughout the whole body.
    As a recent graduate of the nutritional therapist course, I realize how well up-to-date are all your educational materials.
    Thank you again for the wonderful work you do on spreading the good, non-biased, scientific, evidence based information through your school.

    • Nurten – I love your passion for science, your feedback means the world to us! These little microscopic fellows that outnumber our cells by 10 hold the key to many things we’re yet to discover… if only they could talk!

  • Imre Janoshazi

    Reply Reply August 28, 2015


    I really enjoyed reading your review
    I’d be interested in your opinion about two books that I find quite fundamental in regards creating our own diet:
    1. Fit for life by Harvey and Marilyn Diamond
    2. The 4-hour body by Timothy Ferriss

    looking forward reading your further reviews and etc.


  • Christine

    Reply Reply August 31, 2015

    Hi Alex,

    Thank you for the review as I am now learning to understanding how the function of the body works. Very interesting and looking forward to reading and exploring more.

    Kind regard,

  • Gemma Voce

    Reply Reply August 31, 2015

    Hi Alex

    I really enjoyed your review of this book, please do more book reviews. I am currently studying for your Nutritional Therapist course and loving it. Understanding the science has opened my eyes to how and why the human body does what it does and what we can do to keep ourselves healthy. Keep the information coming :) Thanks Gemma

  • Alison

    Reply Reply January 19, 2017

    Very useful to see a critical review. So many health / nutrition books are written with the intention of convincing the reader to do or buy certain things. If you’re not an expert it is very hard to tell what the facts are, whether any research has been done and if so, what the results were and what confidence one should put on those results.

    Your review is a step in the right direction and has persuaded me that this book is not what I want. I would, however, like to read more about the science of gut microbes and healthy eating, and shall be following up some of your links. THank you.

  • Alison

    Reply Reply February 14, 2017

    Thank you!

  • David

    Reply Reply February 24, 2017

    Physics will explain that losing weight is about eating less and moving more, and yet Tim Spector tell us that isn’t what counts…it’s the microbes and our microbiome that cause weightloss or weight gain.

    But you can’t ignore physics, and consuming less calories than you require WILL lead to weightloss…diets therefore are myths, even eating for your microbiome is a myth compared to physics and the calories equation.

  • Sam Hardy

    Reply Reply March 23, 2017

    A friend recently told me to read GRAIN BRAIN to get my FACTS straight. I searched for Grain Brain reviews, and here I am. Now I don’t know what to believe! I have signed up for a free course, and may do a real one…
    I am a director of a CIC – GreenerGrowth, and fascinated by the effects of food as medicine.
    I have recently read GUT by Giulia Enders – be keen to see a review.

    Can I see all reviews on one page? I can’t see a ‘search’ function on your site?

    And Finally…

    I am a direct seller for a US company about to launch their products in the UK. A lot of what they say is similar to everything I read on your site – would you be prepared to look into it?

    • Hi Sam! I think most diet books written for layman audiences often have misinterpreted, oversimplified or exaggerated information. That’s what boost sales, right? So I’d stick to academic/scholarly books and scientific journals whenever possible :-) You can find other reviews we’ve conducted here: Regarding your last question, we’re 100% independent scientists and researchers and we don’t promote third party products, our scientific content is ad-free and we’re very proud of that as we like to maintain an unbiased take on things. Any other questions, don’t hesitate to ask! Best wishes, Maria (THSA team)

  • Micki Jacobs

    Reply Reply September 9, 2018

    There are so many new data about vitamin K2, yet I don’t see anything here. Our microbiomes can make long chain K2, we actually make MK-4 endogenously from vitamin K3, made when we cleave all dietary forms of K (as K1 and K2) in our guts and transport this K3 via the lymph system.
    No K3 in serum.
    No K3 in food.
    But we make it and transport it, but no one seems to know.
    And the enzyme UBIAD1 is essential to make this MK-4 AND it controls cholesterol and calcium.
    A CAC=0 is a 15 year warranty from death by all causes.
    The obesity epidemic in the US began in about 1980…so what happened?
    I think we falsely disparaged saturated fats and then created aberrant additives to replicate the qualities in those high-saturated fat foods such as man-made emulsifiers.
    Polysorbate 80 or carboxymethylcellulose make for impaired mucus layers in our guts which is strongly correlated with T2D.
    In short…we fouled up food, guts, and thus sickened and fattened us.
    NOT genes that have changed.
    But our multi-faceted attacks on guts from everything such as glyphosate, food additives, EDCs, etc are fundamental to our impaired health.

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