Low-carb diets will shorten your life? Fat chance!


By Marika Sboros

Well, here’s a page-turner for the diet books. A new study in The Lancet Public Health claims that low-carb diets could be killers.

These diets increase your risk of mortality (premature death) by shortening your lifespan, say the study authors. In other words, they argue that low-carb diets are life-threatening.

They also claim the same for high-carb diets. But don’t mistake that for any kind of anti-carb stance. On the contrary. Their idea of “moderate” carbohydrate consumption is 50-55% of the diet. They say that’s  the way to go for a long life.

They say that moderate carbs from plant foods up your chances further of avoiding a premature end. And they speak of  “controversy” around low-carb diets. Thus, they claim that low-carb diets containing animal foods are even more of a threat to life and limb than those with plant-based foods.

Overall, they seem to have a serious beef (pun intended) with low-carb diets.

It’s putting it mildly to say that leading doctors and scientists globally dispute those claims. And not just because this is yet another observational study. That is a big problem because, by definition, observational studies are only associational. Therefore, they cannot prove causation.

Study weaknesses

But there are other reasons that this study has left many critics hot under their scientific collars. The kindest they’ve said so far is that we should simply disregard the study and concentrate on “more important” matters. That’s what Dr Luis Correia, director of the Centre for Evidence-Based Medicine in Brazil, thinks of it.

Other experts say that we cannot ignore it because it bears such a strong stamp of approval from Harvard.

Prof Richard Feinman

US biochemistry professor Richard Feinman says that in a field “not known for thoughtfulness”, The Lancet study ranks as “the most intemperate and irresponsible in recent memory”. In an email to me, Feinman calls it “a very ugly moment in the history of medicine”.

He says a big danger in this study is that it will encourage doctors to withhold recommendation for low-carb diets to patients with diabetes despite evidence that these diets are “often a cure”.

Feinman has taken his usual forensic scientific scalpel to what he calls the study’s  “questionable style of bloodless, robot-like computer analysis and acceptance of low hazard ratios” involved.

Fatal flaws

Hazard ratio (HR) is a term researchers commonly use in medical literature when describing survival data. They don’t only use survival data to describe the number of people who survive or die over a period. Increasingly, they also use these data to describe how many people can reach “a certain point in time without experiencing a hazard or event other than death (for example, suffering a heart attack) “. Or conversely, to determine the number that does experience an event.

The Lancet researchers have characterized subjects’ nutritional status on the basis of two food questionnaires separated by six years and an HR of 1.12. This further “violates standards of research integrity”, Feinman says.

He identifies another fatal flaw. The researchers have claimed that low-carb diets are dangerous without actually studying low-carb diets.

“You cannot say that low-carb diets are bad if you have not measured low-carbohydrate diets,” Feinman says. Low-carb diets are already well-established and “do not allow setting up your own straw-man”.

In addition, if you criticize diet or any theory, you are obligated to present the opposing point of view and explain what is wrong with them, he says.

‘Uniquely absurd’

But the most likely “landmark” that makes this study fatally flawed is the claim “that low-carbohydrate diets are life-threatening”, Feinman says. The researchers have made it on the basis of “dreadful analysis”. The HR in The Lancet study was typically below 1.5 that Feinman says makes it “uniquely absurd”. (Some scientists say that a hazard ratio of above 2 is the barest minimum required for any robust conclusions. Others set the bar far higher.)

Click here to read: ‘Pure’ proof fats don’t kill, dietary guidelines wrong? 


British consultant cardiologist Dr Aseem Malhotra is similarly scathing. On BBC World News this week, he called the study “fatally flawed” and a “miscarriage of science”.

Reviewing all the up-to-date evidence shows that low-carb are not dangerous, Malhotra said. And anyone claiming that we should all eat carbs moderately is giving “bogus dietary advice”.

Thus, the real meat of objections to the study includes cherry-picking data – ignoring growing robust evidence to the contrary. That feeds into other major objections that the study lacks scientific integrity at best. At worst, that it could constitute scientific misconduct.

In media interviews, Malhotra says that anyone who tells people to eat everything in moderation is  “either ignorant or paid by the food industry”.

More questions than answers

“Seek their conflicts and you’ll find them,”  he says.

The most effective approach for managing type 2 diabetes is cutting sugar and starch, Malhotra says. And when it comes to the evidence, a  systematic review of randomised trials reveals it: “Low-carb is best for blood glucose and cardiovascular risk factors in both short and long term.”

So, who are the researchers who would have you believe that low-carb diets really are dangerous? On what evidence do they claim that a moderate, plant-based carb intake is optimum for longevity?

Prof Scott Solomon

The study is titled: Dietary carbohydrate intake and mortality, a prospective cohort and meta-analysis. Of the 10 researchers, eight are from Harvard Medical School. Corresponding author is Dr Scott Solomon, Harvard professor of medicine and director of non-invasive cardiology at Brigham and Women’s Hospital in Boston, Massachusetts. The hospital is an affiliate of Harvard Medical School.

The other researchers are from the University of Minnesota.

Among Solomon’s co-authors is another Harvard professor of medicine as well as nutrition and epidemiology (now emeritus) Walter Willett. Willett is as well-known for his advocacy of plant-based diets.

The Lancet researchers studied 15,428 adults aged between 45–64, in four US communities during a median follow-up of 25 years. Their aim: to investigate the association between carbohydrate intake and mortality.

Data came from a dietary questionnaire that participants completed at enrolment in the 1985 Atherosclerosis Risk in Communities (ARIC) study. That questionnaire has raised more questions than answers.

Meat-heavy diets a killer?

In giving background, the researchers say that low-carb diets are a “popular weight-loss strategy”. They also say that the long-term effect of carbohydrate restriction on mortality “is controversial”.

They made it clear that they were only making observations. The researchers said that both high and low percentages of carbohydrate diets were associated with increased mortality. They claimed to have observed “minimal risk” at 50–55% carbohydrate intake.

Click here to read: Sat fat causes heart disease? PURE bollocks! 


They also claimed that low-carb dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality”. And that those favouring plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter and whole-grain breads were associated with lower mortality.

That led to predictably fevered media headlines claiming that “meat-heavy, low-carb diets can kill”. And that cutting back on bread and pasta could shorten people’s lives by up to four years.

A UK report in The Guardian said that it could look like years of scientific study finally proving “what common sense already knew: everything in moderation”. Of course, The Lancet study proves nothing of the sort. If anything at all, it proves that common sense isn’t common.

The same report made a detour into what Aristotle would have said about moderation. However, the author sensibly added the caveat that moderation is not that simple. And even common sense recognises that if “everything in moderation” is true then moderation “also has its limits”.

Conflicts of interest

If Oscar Wilde were around, he would have heartily endorsed that sentiment. Wilde once memorably advised: “Everything in moderation, including moderation.”

Robust evidence for that is available. Britain’s NHS (National Health Service) GP Dr David Unwin has been using low-carb diets successfully to treat diabetic patients. He says that “telling diabetics to eat carbs moderately just leaves them moderately poisoned.”

On Twitter, US psychiatrist and low-carb advocate Dr Georgia Ede says that the new study demonstrates  “complete disregard for mechanistic plausibility”, she says. That’s often to the point of “flying in the face of evolution, biochemistry, physiology, botany and common sense”.

She also noted that the researchers did not include or reference the questionnaire used in the ARIC study as a source of their data.

Weak science, strong personalities

Bulldog investigative reporter US science writer Nina Teicholz has found and made available the questionnaire available. Teicholz is author of The Big Fat Surprise, Why Butter, Meat, and Cheese Belong in a Healthy Diet. It’s a seminal work that many say has changed the face of nutrition science and evidence forever.

Former editor of The BMJ, Dr Richard Smith said that Teicholz did “a remarkable job in analysing the weak science, strong personalities and vested interests in political expediency” that have characterised nutrition science.

Critics say those elements are at work in The Lancet study.

Teicholz has dismissed The Lancet study is based on “weak epidemiological data that relies on self-reported data”. These data are notoriously unreliable and shown to be correct only 0-20% of the time, she says

Robot-like analysis of low-carb diets


Click here to read: Teicholz: How low-fat diets can kill you


British obesity and public health researcher Dr Zoë Harcombe says that the study has generated “irresponsible global headlines”. In an article on her website, Harcombe highlights the study flaws behind the headlines.

Epidemics of obesity and type 2 diabetes show no sign of abating, she says. Therefore, it is “unhelpful, to say the least,” to encourage consumption of at least half of one’s diet in the form of the one non-essential macronutrient (carbs).

One of the flaws she identifies is that the researchers have chosen groups for carb intake and consumption subjectively. “Not even the carb ranges are even,” she says.

Most groups covered a 10% range (eg 40-50%). However, the range chosen for the “optimal” group (50-55%) was just 5% wide, Harcombe says. This placed as many as 6,097 people in one group and as few as 315 in another.

Massaging data

Thus, the subjective group divisions introduced what Harcombe calls “the small comparator group issue.” She explained the dynamic in the recent whole grains review. Harcombe repeats and builds on the explanation because she says it’s crucial to understanding The Lancet paper:

She gives as an example: If 20 children go skiing – 2 of them with autism – and 2 children die in an avalanche – 1 with autism and 1 without – the death rate for the non-autistic children is 1 in 18 (5.5%).  And the death rate for the autistic children is 1 in 2 (50%).

This demonstrates “how bad (or good) you can make things look with a small comparator group”, Harcombe says.

Click here to read: Naudé review: mistake or mischief against Noakes?


She also explains how the researchers managed to move from subjective grouping to the sensational life-expectancy headlines. They applied a statistical technique (called Kaplan-Meier estimates) to the ARIC data. “This is entirely a statistical exercise,” Harcombe writes. After all,  we don’t know when people will die. “We just know how many have died so far.”

This exercise resulted in the researchers’ estimates of longevity improvements:  They write that they “estimated that a 50-year-old participant with intake of less than 30% of energy from carbohydrate would have a projected life expectancy of 29·1 years. That’s compared with 33·1 years for a participant who consumed 50–55% of energy from carbohydrate.

Similarly, they estimated that a 50-year-old participant with high-carbohydrate intake (>65% of energy from carbohydrate) would have a projected life expectancy of 32.0 years. That’s compared with 33.1 years for a participant who consumed 50–55% of energy from carbohydrate.

Making mischief

 In this way, Harcombe says that the researchers used the small comparator group extremes (<30% and >65%) to “make the reference group look better”. It’s an example of “the mischief you can make when you subjectively make up groups”.

She returns to the example of the skiing children: If we were to use the data we have so far (50% of autistic children died and 5.5% of non-autistic children died) and to extrapolate this out to predict survival, life expectancy for the autistic children “would look catastrophic”.

This, Harcombe says, is exactly what has happened with the small groups – <30% carb and >65% carb – in The Lancet study.

In other words, she says that the researchers have manipulated the data. And as any good scientist will tell you, that’s just not on.

It would help, Teicholz adds, if the media would “stop reporting on these kinds of (sensationalist) findings”.





    Making “Low Carb” a Murderer – Part 1 of 2 – Mischief & Manipulation
    Derek Tran
    August 20, 2018

    Making “Low Carb” a Murderer – Part 2 of 2 – Broken From the Start
    Derek Tran
    August 23, 2018


    Low carb diets could shorten life (really?!)
    August 23, 2018 association, carbohydrates, causation, epidemiology, Harvard, meta-analysis, relative risk

    Carbs, Good for You? Fat Chance!
    Dietary dogma’s defenders continue to mislead the public and put Americans’ health at risk.
    By Nina TeicholzSept. 11, 2018 6:36 p.m. ET

    Scientific attack on low carb diets: Why the healthy low carb community shouldn’t be swayed by the latest Lancet Public Health study
    22 August 2018
    Robert Verkerk PhD, scientific and executive director, ANH-Intl

    The collapsing edifice of nutritional science: Could reserach be made to work in the interests of the public rather than corporations following the latest scientific attack…
    29 August 2018
    Robert Verkerk PhD, scientific and executive director, ANH-Intl

    When Bad Science Can Harm You
    Angela A. Stanton, PhD
    August 17, 2018

    The Ripple-Effect of Bad Science
    Angela A. Stanton, PhD
    August 25, 2018

    Low carbs and mortality
    John Schoonbee, PhD: Global Chief Medical Officer at Swiss Re
    Published on August 20, 2018

    Will A Low-Carbohydrate Diet Kill You?
    Adam S. Nally, D.O.
    AUGUST 20, 2018

    New Study Links Low-Carb Diet to Earlier Death: Here’s What It Gets Wrong
    August 21, 2018

    Do low-carb diets lead to early death? (The ARIC/Lancet Study Explored)
    Ken D Berry MD
    Published on Aug 19, 2018

    David Harper: Keto diet a healthy alternative to the standard Western diet
    Updated: August 23, 2018

  3. Another pachyderm in the parlour, playing at being invisible…
    What is the point of lingering on the land for a little longer, if the price paid is in NOT ‘Living’ ?
    Better a glass of wine shared with Family & Good Friends than soul-less starvation. 🙂

  4. Why did this ‘study’ receive such prominent media coverage? Much bigger and better studies barely get a mention.

    A Canadian study showing benefits from eating red meat and dairy products got a small item in today’s Times, but nothing on radio or TV. I wonder if deliberately confusing the picture isn’t part of the strategy to keep us eating a so called ‘balanced’ diet. You know, the low-fat, 50 – 60% starchy-carbs one that has made us all so slim and healthy.

  5. Here is a SA journalist that also needs a bit of education


    “Scientists including South Africa’s Tim Noakes have become increasingly vocal about the health benefits of low-carb high-fat diets in combating obesity and linked chronic conditions such as cardiovascular disease‚ hypertension‚ type 2 diabetes and cancer.

    But the long-term safety of these diets is controversial‚ with previous studies reporting conflicting results of their influence on the risk of cardiovascular disease‚ cancer and death.”

  6. Walt Wallet. Say no more.

    Fascinating to watch this study being eviscerated, and rightly so. One wonders why the peer reviewers failed to notice the flaws. Perhaps they are all vegans and needed an urgent antidote to the recent conferences from which you reported.

  7. Sigh. In addition to the horrible analysis of the study . . .

    The “low-carb” quintile was 37% carbs. That would be 185 grams in a 2,000 calorie diet – 60+ grams per meal (at 3 a day). NOT low-carb.

    The mean BMI for all groups is 27.4 or over. Calories consumed ranged from 1558 to 1660. The “low-carb” quintile had the lowest calories consumed (1558) and the highest mean BMI (28.0). Even if one thinks that Food Frequency (should be Fantasy) Questionnaires are a valid way to gather data (as the authors of the study seem to do; I think “Garbage In, Garage Out”), the low calories consumed alone (and then in conjunction with BMI figures) should have made them see that the data is horribly, horribly flawed.

    As someone else pointed out, there’s nothing considered about alcohol consumption.

    It just astounds me that (if you’ll pardon my language) crap like this is published and taken seriously. It would be a joke if it was not treated seriously by the media and much of the world.

  8. I think there’s something badly wrong at ‘The Lancet’ and I no longer consider it to be trustworthy. They seem to print anything favourable about statins and other dross science like this ‘study’ that reinforces the current nonsense. Food diaries and weak associations, for goodness sake!

    Does any study of low-carb diets ever actually look at real low-carb? The disgraceful Naude review didn’t and this seems to be a consistent tactic.

    • It’s been pointed out that Lancet Public Health is actually a pay-to-publish journal. Nevertheless I agree, they will post almost anything that supports Conventional Wisdom, unlike the BMJ journals which are a bit more questioning.

      It’s interesting how things seem to be moving in both directions at once, and how the likes of dieticians are jumping desperately on absolutely everything that supports conventional wisdom, and of course veganism while finding every excuse to dismiss the likes of VIRTA. You’d almost think they were paid to do this.

  9. The Lancet has, in my estimation, lost it’s edge… and not worthy of a serious comment. So I’ll restrict myself to the observation that Pandas manage to be nice and cuddly on a purely vegetarian diet. – except to bite the odd human. But since most of those are Researchers and/or Zoo visitors seeking fame on You Tube…

    I can’t speak for everyone else, but there’s no way I’m still eating the same foods and amounts thereof… had I self-reported in a survey, 25+ years ago.
    Especially if the survey was, um, inaccurate.

    A Pile of old papers don’t strike me as a firm foundation to build anything upon, – but the graphs look Impressive.!

  10. Even if we take the data and HRs at face value we are left with a question – what about alcohol? Doesn’t it matter when considering longevity?

    “Of all macronutrients, carbohydrate intake was the first to decrease with increasing alcohol consumption. In the multivariate analyses, the level of alcohol consumption was found to be an independent predictor associated with lower intake of other macronutrients.”

    “Per capita distilled spirits consumption turns out to be the strongest determinant of the adult male mortality rate in Europe as soon as the unrecorded alcohol consumption is taken into account.”

    In ARIC, alcohol was associated with type 2 diabetes, heart failure, and so on, so they did measure it. But then they completely failed to adjust for it or even mention it, as a macronutrient or a food in the current paper. But, even so, alcohol is always under-reported, of course, so Seidelmann et al should have adjusted for accidental death/violent death/suicide/execution (yes this is a category in the US!) in my opinion.
    You can see that if you adjust for the behavioural effects of alcohol on mortality in another study, NIH-AARP, the associations of red meat with various other causes of mortality completely disappear. I suspect something similar would happen here if we had the carbohydrate and accidental death HRs for ARIC.
    “The associations between unprocessed red meat and accidental death in men, HR 1.26 (1.04-1.54), were as great (albeit with slightly wider CIs) as the associations for cancer mortality, HR 1.22 (1.16-1.29) or CVD mortality, HR 1.27 (1.20-1.35).”

  11. Totally irresponsible headline, but what can you expect from journalism whose sole function is to sell papers and the advertising that goes with them. The whole point is that at some time we will all die and from some cause or other, even just ‘old age’ and breakdown of bodily functions. Yes, there are certain lifestyles that will shorten lives (alcohol or drug addiction), but how is it possible to categorise a huge variety of lifestyles as more or less inclined to prolong or shorten a life. The idea is to eat a diet and live a life that produces the maximum health outcome and not worry about when you ‘go’. Genes have an enormous role to play as does the fact that you may end your life in a car crash at a young age or have a huge heavy object fall on you.

    Love Zoe Harcombe’s thinking….right to the point.

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