Sugar versus fat: why so many scientists got it so wrong for so long

Looking for more background when I was writing previous post, I came across a very lengthy, but nevertheless interesting story in The Guardian. This long read is titled The sugar conspiracy and the subject is the battle between the theory that sugar is the (main) reason for the obesity epidemic and the established theory that fat was the culprit.

This is not something recent, the controversy originated already in the middle of last century and, although the fats theory was found to be ultimately wrong, the sugar theory was ridiculed, discredited and careers were ruined. It took fifty years for the theory to resurface, leaving the question why the top nutrition scientists got is so wrong for so long.

We hear that objection often in climate change discussions: so many scientists can’t be wrong for so long. Well, it is possible and the sugar theory is only one of its manifestations.

The most interesting part of the Guardian story is the tension between the scientist who first proposed this theory (John Yudkin) and his scientific adversary (Ancel Keys). It reads like the current controversy on climate change. Replace Yudkin with your favorite skeptic, Keys with your favorite alarmist, fats with CO2, meat/dairy/sugar industry with Big Oil/Tobacco and the story sounds really modern. There are a lot of similarities between how the scientists in the two sciences treat those who are skeptical towards the consensus position.

This is the part that struck me the most (my emphasis):











“I believe both those things,” replied Yudkin.


Remember, Keys was wrong all along, while Yudkin was right.

Later in the article there was also this (my emphasis):


Scientists are social beings after all and prone to biases. What I find striking in the article is the recognizable way the consensus science was portrayed and how the competing theory was dismissed/ridiculized. There was the unwarranted certainty in which the saturated fats theory was brought, its institutionalization, the official advice, the uncritical attitude towards the consensus position, the one-sidedness, the reluctance to debate, the role of the media and so on. It is interesting to see how a consensus can survive for such a long time, even if it is based on obvious flawed research, even with peer review that should prevented this issue.

I also like the idea that even an entrenched consensus was eventually seen for what it was: flawed and based on cherry picked facts. It took a long time though. Nor Yudkin nor Keys lived long enough to see this consensus overthrown.

Does it mean that climate science is wrong because there was this much defended consensus in nutrition science that after half a century turned out to be wrong? Not necessarily. Those two controversies have their similarities, but are logically not related. It is not because there are resemblances between the two that the outcome will be the same. The story just learns us that the ruling consensus can be wrong, even if this specific consensus position is held even for a long time and even if there are checks and balances in place. The consensus position is not the reliable construct that it is painted as.


3 thoughts on “Sugar versus fat: why so many scientists got it so wrong for so long

  1. manicbeancounter

    This is a great article. But there are other lessons for the climate disputes apart from that the ruling consensus can be wrong.
    Oneis that if you want to understand how well a hypothesis relates to the real world, the answer always lies in the real world and not in the numbers who believe or disbelieve in that hypothesis. To properly understand – or at least to get the best possible understanding – it is important to look at different data sets and at the different conclusions that it is possible to derive from different methodologies.
    Also, when there are different theories, it is possible to compare and contrast how well they fit the data. Having studied economics, it is an important aspect to look at the limitations of the theories, and that can often only be accomplished through competing ideas. Sometimes a synthesis can be developed, or at least common ground reached.


  2. poitsplace

    Yes, this sort of thing, along with shoddy studies used for regulation, made me realize that we cannot plan our lives around minor percentages in studies. One cannot reasonably claim to have found anything to be true with statistics with at 95% “certainty”. We need to watch for profound impacts. Nobody works with statistical certainty when talking about gravity. Nobody works with statistical certainty when dealing with the existence of a disease.

    And a good example of how we (including scientists) delude ourselves. I saw a video earlier today where a woman was talking about science “denial”. And in one of her examples she said she’d stopped working with the discovery channel because after the show she’d been in about martian life had aired, they showed something on aliens or alien abductions.

    But because of the fact that we literally have ZERO evidence of life on Mars, anything she or any other scientist said would be nothing but speculation. And her comment made it obvious that she wasn’t entirely aware of this distinction. She then went on to talk about climate change and how absolutely certain it was, touching on topics that she clearly was completely ignorant of (like the fact that the error bars on GRACE satellite measurements make almost all of the observations questionable, rates of sea level rise, etc). And on her part that amounts to faith in science.



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