The latest ‘science’ on sugar is so flawed it tells us nothing whatsoever

Robert Lustig is a Californian scientist and anti-sugar campaigner who became a minor internet sensation with his YouTube video, The Bitter Truth, which portrayed sugar — and fructose, in particular — as the driver of obesity and diabetes. Today, he published a study which, he says, proves his highly controversial hypothesis that a ‘calorie is not a calorie’. He has also been given a column in the Guardian in which he calls for a sugar tax. Unfortunately, the evidence he presents is just awful.

The aim of Lustig’s nine-day experiment, which involved 43 obese children, was to see what happens when someone maintains their calorie intake but reduces their sugar consumption. Mainstream scientists would expect to see no change in body mass. Lustig expected to see weight loss, and he did.

There’s a simple way to conduct a study like this. Give half the kids a 1,500 calorie per day diet that is high in sugar and give the other half a 1,500 calorie per day diet that is low in sugar. Make sure they eat it (don’t just send them home with it, as Lustig does) and see what happens.

Alas, that’s not how Lustig went about things. Instead, he asked 43 fat kids what they usually ate and then gave them an equivalent number of calories in low-sugar meals for nine days. At the end of the period, he observed an average weight loss of 0.9 per cent. Bingo! A calorie from sugar is more fattening than a calorie from pizzas, crisps, hot dogs, popcorn and burritos (for that is what the low-sugar meals consisted of). Tax sugar now!

Not so fast. There are at least two critical flaws in this experiment which render it worthless. First, Lustig took the kids’ evaluation of their usual diet on trust, despite it being well known that everybody — especially obese people — under-report how many calories they consume. If the kids said that they usually ate, say, 1,600 calories when they really ate 2,200 calories then the 1,600 calorie diet Lustig put them on would be bound to induce weight loss diet regardless of its sugar content. As Tom Sanders, a professor of nutrition and dietetics, has pointed out, the kind of weight loss seen in the nine days of this experiment would require an energy deficit of over 600 calories per person per day. Either the laws of thermodynamics are wrong or Lustig’s child subjects under-estimated how much they normally eat. The latter explanation is vastly more probable than the former.

Secondly, there was no control group. This is such a basic requirement of a scientific experiment that its absence is astonishing. We need to know what would happen if a group of similar children were given a high-sugar diet containing the same number of calories as the low-sugar diet. If, as is highly likely, the kids under-reported their normal calorie intake, the use of a control group would have exposed this flaw because both sets of kids would have lost weight, regardless of how much sugar was in their diet.

This small, uncontrolled study, which made no attempt to verify what its subjects normally eat, tells us nothing useful whatsoever. The claim of the Guardian‘s headline writer that ‘the science is in’ would be laughable if it were not so depressingly typical of the standard of scientific analysis in the popular press.

  • lolexplosm

    It worries me that such an obviously poor study got past peer review. Unfortunately it doesn’t surprise me that this receiving as much media attention as it is.

  • Zarniwoop

    What worries me is that the dumb ass media crawled all over this junk science and showed it as gospel!


  • Summer Isles

    The study was done by a Professor of Paediatrics whose knowledge of managing childhood obesity is perhaps greater than that of Mr Snowdon who I believe was an historian before becoming a reporter.

    The work was done in a clinical outpatient setting. A passing acquaintance with these matters would reveal that many clinical trials are done without controls because it is impractical or unethical to subject patients, especially children, to the kind of restrictions which controlling involves.

    The essential point of the research is that glucose interacts with the body’s metabolism in particular ways that produce insulin resistance. This is well explained in the following link.

    • lolexplosm

      Perhaps greater yes but an appeal to authority with an author with essentially unproven views that go against the consensus doesn’t really work. Plus I think that’s essentially an ad hominem and, though I might not be seeing it, I fail to see how the purpose of this study was to test glucose’s interactions and insulin resistance. Lustig’s research and theories seem to focus on fructose, at least initially.

      Any decent clinical trial will have a control, ethics rarely enters into it e.g. vaccines. When you trial a new drug you trial it against a placebo or the current standard of care vs the drug. The point of a control is that there is no real change exerted on a control group. Ethics can’t really be of concern to effectively a placebo group particularly one involving isocaloric intake meaning there is no real excuse for not having a control group in this study.

      Such a study may be of genuine interest but without a control group, and the other severe limitations of the study, the conclusions drawn cannot be made yet Lustig does so. Mr Snowdon is simply echoing the criticisms made by the majority of the scientific community and reflects the scientific consensus which the vast majority of the media seem to have ignored.

      If Lustig can replicate his conclusions in a larger, more controlled and rigorous study, then we will all be very interested to see it as it will fundamentally change our understanding of biology.

      • Summer Isles

        It’s not ad hominem to draw attention to someone’s lack of qualifications or experience in an area on which they are expressing a trenchant view.

        I am entitled to express a view on the correct way to land a 747 but I would expect most people to prefer the opinion of a pilot.

        The practical point is that Professor Lustig sits in a clinic every week and advises patients about their health. He has established that changing his advice, in relation to glucose intake, appears to change the patient’s clinical features by way of BMI, cholesterol and insulin resistance.

        If his results are replicated that may be an important step forward for his key audience which is the thousands of other doctors who sit also sit in clinics every week, advising overweight patients on how best to improve their health.

        The fundamental biology is a different ball park and the fact is that no-one properly understands the relationship between glucose and insulin. That doesn’t mean that front line clinicians should stop publishing and sharing their experience with other clinicians.

        • lolexplosm

          So unless a journalist or author has the relevant experience or qualifications, they can’t research the evidence and present their findings on the matter? Tell that to Taubes and Teicholz. Instead of addressing his points, whether they are right or wrong, you suggest he shouldn’t make them in the first place i.e. an ad hominem.

          Mr Snowdon is echoing the criticisms made by Lustig’s peers, don’t shoot the messenger. These criticisms are very valid and quite rightly significantly reduces the impact Lustig claims his study has. Unfortunately the criticisms haven’t received as much airtime as the study itself.

          • Summer Isles

            The problem is that without some knowledge of a subject you end up looking at matters from a perspective that is fundamentally misleading. There are good journalists who can educate themselves on a technical subject to avoid this it requires time and reading.

            The report is first and foremost a clinical report based on outpatient experience. Its essence concerns the effects that changing clinic advice has on overweight patients.

            Snowdon complains that Lustig took his patient’s accounts ‘on trust’. That is how medicine works. Doctors are not detectives, from a practical point of view you have to accept what patients tell you as truthful. The vast majority of patients do their best to be truthful when dealing with healthcare staff.

            He talks about control groups. In order to have a control group Lustig would need to have confined two groups of 43 children to a hospital ward for over a week and observed everything they ate. You don’t need to be a paediatrician to see the practical difficulties this would pose.

            What would happen to the patients who normally use those wards ? Who would be responsible for the children’s welfare ? What would the parents think ? and so on.

            He invokes the Second Law of Thermodynamics, heaven help us. These kids were seen in clinic, weighed and had bloods. Nine days later they were weighed again and had cholesterol and other checks repeated. They has evidently lost weight and seen improvements in cholesterol. Whether Snowdon likes it or not that is what is reported as having happened.

            Lustig is onto an important truth which is that simple carbohydrates like glucose are metabolised in a way that is very different from the metabolism of more complex carbohydrates like starch. There is a great deal of research going on into this that cannot be reduced down to headlines for and against sugar.

          • lolexplosm

            Sorry but it seems to me that you think Lustig is infallible as perhaps he fits in with what you already believe i.e. already claiming him to be “onto an important truth”.

            Forget Snowdon, look at the criticisms of his “study” by the relevant experts here:


            and here:


          • Summer Isles

            You aren’t reading what I have said and you really need to do better than fall back on ancient tropes about infallibility.

            No where have I claimed that Lustig is infallible, in an earlier post I said clearly that we don’t fully understand glucose metabolism.

            The link you have made sets up straw men arguments by misreading what the research actually sets out to do.

            What is being controlled for is the advice given in clinic and what is being measured is the how the weight and cholesterol and other results and affected by that advice.

            That is what matters in a clinical setting to the people who do the day to day work of managing patients with obesity.

          • lolexplosm

            You don’t think he’s infallible but seem to refuse to accept any criticism and limitiations of this study? If his results were that significant, the critiques wouldn’t be as severe as they are. It does and it doesn’t warrant further work because it was a flawed and limited study. If the results are repeated in a much more controlled way then Lustig will certainly open up a new direction of research.

            I read what you said and disagreed with it and to be frank, and no offence, it shows somewhat a lack of understanding e.g. Snowdon is not suggesting Lustig lied but it’s likely that the kids did because it’s well accepted when people self-report intake of anything, whether food, smoking, alcohol etc and particularly in children, it’s significantly lower than reality. As you are not really interested in Snowdon’s opinions, I linked to what the experts in their relevant fields say about the study.

            If you find anything wrong with the links, I’d be curious to hear a criticism of the criticisms so to speak.

          • I for one AM ‘suggesting’ that Lustig lies. It’s a grotesque lie, an obvious lie, and I’m amazed that he thinks he can get away with it. Sugar is not toxic. Only the dose is — and that is true of anything.

        • Lustig is an anti-sugar crank. Your swipe at Snowdon won’t stick: critical judgement is critical judgement. Doctors and scientists are often wrong despite their good intentions; nutritional science as with behavioural science is a fraught, highly politicized field and both are plagued by selective cherry-picking, bias, and in some cases outright fraudulence; and many people, such as Lustig, have agendas that go well beyond the scientific facts of the matter. So you can take your patronizing attitude elsewhere.

          • Summer Isles

            There is nothing patronising about trying to establish whether people actually know what they are talking about on a technical matter.

            Nor am I suggesting Lustig’s research is flawless, that is another straw man.

            I am all for critical judgement. Perhaps you and others would like to share your judgement on the attached paper on glucose transport mechanisms at a cellular level and its impact on insulin resistance, the link is here :


            It requires a bit of technical knowledge but, since I am anxious not to seem patronising, I am sure you will have no difficulty understanding it. If by some chance you don’t then I should not be so rude as to invite you to take your lack of knowledge elsewhere.

  • Summer Isles

    The study was done by a Professor of Paediatrics whose knowledge of managing childhood obesity is perhaps greater than that of Mr Snowdon who I believe was an historian before becoming a reporter.

    The work was done in a clinical outpatient setting. A passing acquaintance with these matters would reveal that many clinical trials are done without controls because it is impractical or unethical to subject patients, especially children, to the kind of restrictions which controlling involves.

    The essential point of the research is that glucose interacts with the body’s metabolism in particular ways that produce insulin resistance. This is well explained in the following link.

  • Lustig is an unscientific Left-leaning man (as is quite clear from his book on sugar, which I returned for a refund), who claims that sugar is a toxin, pure and simple (his language). Well, no it isn’t: that is a lie and he is a liar. Anything can be toxic if you have too much of it, and that includes plain water. I notice that Julia Manning of Health2020 makes the same scaremongering false claim that ‘alcohol is a toxin, the risks outweigh the benefits’. Says WHO? This factless nannyish sweeping statement comes just after she has condemned a doctor who is actually an expert in the subject of alcohol consumption for being ‘unhelpful’ (in The Independent, see link below). Well I suppose that for a freedom-hater like her, the reality that adults can and should decide what are the risks and what outweighs them is of course ‘unhelpful’ (as are actual facts). She says that the doctor makes grand claims he can’t back up — I’m certain he can, he’s studied years worth of medical science after all — but it’s perfectly OK for her to make grand claims, and ones that disrespect the public, to boot!

  • I’d like to add that Lustig’s book, Fat Chance, is full of fatuous claims. He completely ignores the presence of DIET (i.e. sugar-free) soft drinks, and bashes fast-food chains furiously, when it turns out (as he is compelled to admit) that one of the top five items sold by McDonald’s is in fact DIET Coke. He also wilfully ignores the fact that it has never been easier to eat healthily in so-called fast-food restaurants than it is now: salads abound! He assumes — merely assumes — that everyone eats junk food and dines at these restaurants much of the time. There is no evidence at all for this, though there is plenty of evidence in his book that he really doesn’t like companies very much. He also believes that advertising is somehow evil, which is pure crankery. Of course, I’m sure he doesn’t mind coining it in by writing books that no one knew of before they were advertised. So the man’s a hypocrite, as well.

    He is also a slack reporter of other facts. Notably he says that high-fructose corn syrup is half fructose and half glucose and is thus just like sugar (sucrose). If he says anywhere that HFCS is actually 55% fructose and 45% glucose, I missed it. That extra 5% is significant because it’s the fructose in sugar that causes the most serious problems. HFCS is actually worse than ordinary sugar for that reason. Lustig also claims that ‘other foods that never had sugar before are now busting at the seams from the sugar (e.g. yogurt, ketchup)’. Really? Ketchup never had any sugar before now? I don’t believe it. Also, plain yoghurt continues to have no sugar but most people find it inedible without adding *some* sort of sweetness, once they’ve got it home. They control the sweetness and the source: that hasn’t changed.

  • Callipygian

    Three times and I’m out, but I do want to make a further observation on the substance of this article. That is: weight as such is not really the crucial measure. What is much more important for both long-term and short-term health is body composition. This is why a study of calorie partitioning would be more significant and helpful than a study that just shows weight loss. Of course cutting sugar will cause weight loss in those that previously consumed a lot of it: that is already known. We didn’t need a ‘study’ of 43 people to tell us that. What would be more helpful is to look at what sorts of food lead to fat partitioning and what sorts of food encourage lean mass while discouraging fat storage. But then again, we don’t really need a ‘study’ for that, either. What we need to do is listen to bodybuilders: they clearly have the answers already, and have for decades.

  • Diets X exercise X metabolism X climate X demographics X common sense ( or lack of ) + weight loss or weight gain.
    A doctor told me I would have to lose about twenty pounds weight. I asked him for a diet chart and he said:
    ” Eat half as much, drink half as much beer, walk twice as much, only faster” and come back in six weeks. I lost over twenty pounds.