The case against sugar isn’t closed. But we do have astonishing new evidence

News & Analysis

5th November 2015

My Spectator Health colleague Christopher Snowdon has strongly criticised Professor Robert Lustig’s case series, published last week, about the effects of reducing fructose in the diet. The study had no control group, he says, and relied on information provided by participants about their daily diet — its conclusions are therefore useless. I beg to differ.

On its own, the study doesn’t prove anything. It doesn’t prove that sugar is the cause of obesity. That caveat aside, the results were astonishing.

To recap: over the course of nine days, volunteers were encouraged to follow their previous dietary patterns, with the proviso that fructose, as a percentage of total calories, was not to exceed 14 per cent. Overall the amount of carbohydrates in the diet was to remain the same as was the calorie content. Participants were guided as to what to eat and supplied with food by the research team.

What happened? Researchers noted highly statistically significant decreases in LDL (‘bad cholesterol’), triglycerides and insulin levels. Glucose tolerance (the ability of the body to handle a glucose load, a marker for impending or current diabetes) improved too. Blood pressure, another important marker, was also seen to improve.

Were such changes to be sustained over the long-term we are talking about a significant decrease in the development of subsequent diabetes, heart attacks, strokes and, potentially, cancer.

What makes this even more interesting is the fact that, in patients like these, the most spectacular biochemical effects are usually seen when a low-carbohydrate diet is followed, something this protocol certainly wasn’t.

An average of 0.6kg weight was lost, even though participants were eating with the goal of weight maintenance. In the absence of a caloric deficient, most participants lost weight. (It should be clarified, though, that this loss was not fat loss and could simply have been a transient event.)

The study, of course, has far from proved direct causality; no one is pretending that fructose is behind the obesity epidemic in isolation. But it seems to show quite spectacularly that, without any other intervention, a substitution of a carbohydrate found in almost all processed foods with another can be associated with significant changes in health parameters in unhealthy children and young adults.

The potential ramifications of such a substitution are huge if the study is replicated, something mandatory before any concrete claims can be made or clinical practice changed. Nevertheless, more evidence has been supplied that the traditional paradigm requires further reappraisal.

The case is still open about the consumption of excess refined sugar. But this study is an interesting piece of evidence.


  • Summer Isles

    Thank you for some good sense.

    No one really understands how glucose and fructose are metabolised at a cellular level or their effects on insulin. The medical scientists still have a great deal to unravel.

    However, from the perspective of a practising doctor, Professor Lustig’s work suggests a way forward in the day to day treatment of metabolic syndrome and diabetes that could make a huge difference to the well being of patients.

    That matters more than some of the hot air the blows around these issues from people who have barely the faintest idea what they are talking about.

    • Tarek

      I heartily agree; the answers are on the page in our 2nd year medical school biochemistry textbook detailing the actions of insulin on cell metabolism. Sadly, the truth is hiding in plain site, obscured by misinformation aided by otherwise intelligent people willingly and enthusiastically suspending their critical faculties and insisting the earth is flat. Don’t of course get me started on the scientifically illiterate who wear their ignorance as a badge of pride

      • Summer Isles

        I recall being told that half of what is written in university textbooks is lies, which is perhaps an exaggeration but they generally represent an imperfect summary of thinking over the ten years before they were written.

      • I don’t think the truth is hiding in plain sight any more: Gary Taubes’s books have been out for years and every bodybuilder and athlete is aware of the controversies and the practical facts.

        What I for one object to about Lustig is his patronizing attitude to other grownups and, above all, his unscientific propaganda against sugar as being ‘a toxin, plain and simple’ (I quote). It seems that in the case of nutrition, there is always someone (hello, Ancel Keys) willing to throw mama under the bus for their pet obsessions. This does no one any favours.

        The study is no surprise and no help: it establishes nothing new. Most interested people, never mind doctors, know that refined carbs are especially fattening and that sugar is the Queen of the Refined Carbohydrate (yes, and I’ve read John Yudkin as well). But to tell lies in this fashion is neither needed nor justified.