Guyenet refutes the idea that sugar causes obesity

Assume that each year you gain an amount of body weight that is directly proportional to the amount of sugar you eat. Or, in other words, if you consume 100 g/d of sugar and you fatten a few kilos, if you eat 50 g/d of sugar, you fatten half that amount.

Suppose you’ve been consuming more and more sugar and you were getting fatter. Your consumption peaked at 110 g/d. Nevertheless, in the last 15 years your consumption has gone down progressively, and today you are eating a little less than you used to: 95 g/d. What is the expected evolution for your body weight? Under the assumption that sugar is making you fatten, your body weight is expected to go on rising, but at a slightly lower rate.

That is what I show in the graph below, created assuming that fattening is directly proportional to sugar intake. The blue curve represents sugar consumption (grams/day); the stars show what the body weight would have been in case we hadn’t changed the sugar consumption trend 15 years ago; the orange curve shows the actual body weight evolution (assuming that instead of consuming more and more sugar, we have progressively and slightly reduced our consumption in the last 15 years, as indicated by the blue curve):


Again, if sugar is fattening, what effect would be expected if our consumption were reduced? We would keep getting fatter, but at a slightly lower rate. That is what the orange curve in the graph above confirmed.

A few days ago (see) Stephan Guyenet, PhD wrote an article trying to refute the idea that sugar is fattening us. In his view, the explanation is simpler than that: we eat too much unhealthy food because we like it. His is just another version of the pseudoscientific energy balance theory.

One of the arguments presented by Guyenet is that added sugar intake has declined between 1999 and 2013, but the percentage of adult obese has not. He says, those facts make «highly unlikely» that sugar is the primary cause of obesity. This is the graph he uses as proof:

His reasoning is that if consuming 110 g/d of sugar makes us fatten, consuming between 95 and 110 g/d should make us lose weight! Since epidemiological data says we kept getting fatter and fatter, he concludes that  sugar is «highly unlikely to be the primary cause of obesity».

Americans have been reining in our sugar intake for more than fourteen years, and not only has it failed to slim us down, it hasn’t even stopped us from gaining additional weight. This suggests that sugar is highly unlikely to be the primary cause of obesity or diabetes in the United States, although again it doesn’t exonerate sugar.

What he is saying is that if hitting your head against the wall ten times produces pain, hitting your head against the wall only nine times shouldn’t be less painful, it should be pleasant. If you realise it is not pleasant, if you realise nine times is still painful, albeit to a lesser extent than doing the same ten times, this suggests that there is no relationship between the hitting against the wall and the pain you suffer. Extremely stupid reasoning.

Moreover: between 1980 and 1999, sugar consumption was in the 85 to 110g/d range and people gained weight. Guyenet says that between 2000 and 2013, when sugar consumption was between 95 and 110 g/d, body weight should have decreased.

On the other hand, note that Guyenet interprets data from the graph as if it were a controlled experiment, when it is just observational data. No controlled experiment was carried out.

Note also that the y-axis for the blue curve in Guyenet’s graph doesn’t begin with zero g/d, and this makes the decrease in sugar intake seem greater than it actually is.

Edit (1/18/2017): there is a second part of this article, providing a more thorough explanation:
If your today’s sugar intake is lower than yesterday’s, do you slim down?


Further reading:

  1. puddleg58

    This remind me of when I was an addict on methadone. One year I managed to reduce my dose from 110mg per day to 95mg per day. I was surprised to find that I was still addicted, still constipated, and still suffering from toothache and infections; that I not only didn’t feel better, I actually felt worse, because I had by then been addicted for one more year, and there is an effect of time on the course of toxicity.
    As in this case – there is an effect of time, not just of quantity.

    • Vicente

      Hi George,
      I don’t disagree with you. For sure «time» or «obesity degree» should be part of any accurate model of the effects of sugar on body weight. It wasn’t my goal to formulate such a model: I just wanted to explain, keeping my explanations as short and simple as possible, that Guyenet’s argument is absolute nonsense. The idea that when two variables are related, if one of them decreases the other one has to decrease as well, is inappropriate for someone who holds an academic degree.

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  3. Drifter

    Slightly off topic, but my first question was if the graph in question showing a reduction in sugar consumption is even correct. I wouldn’t trust the USDA on anything and I think NHANES was a food recall survey? If that is the case the participants would have had to know all the names of things which are disguised sugar such as evaporated cane juice, etc. Maybe I’m mis-remembering however, One would also have to know what the supposedly removed sugar was replaced with and whether is was metabolically different than sugar, such as would it up-regulate fat burning or not…

    • Vicente

      Hi Drifter,
      I understand your objection. The problem with that idea is that someone could argue that even if these data are not perfect, they show a trend that should have clearly affected the percentage of obese adults. And my point is that even accepting these data as reliable, ——under the assumption that sugar is fattening— a good correlation between DAILY sugar intake and CUMULATIVE TOTAL percentage of obese adults is not to be expected. The relationship between those parameters is not supposed to be a direct one.

      If sugar is fattening we would expect:
      ANNUAL sugar consumption —> ANNUAL increase in the percentage of obese adults

      For example, using data from sugar-sweetened beverages (SSB) calories per day we can see that when those SSB calories are low obesity grows slowly but when the intake has been higher, obesity (i.e. body weight) growed quickly. The CUMULATIVE TOTAL percentage of obese adults (the same data as used by Guyenet in the orange curve from his graph) versus the CUMULATIVE TOTAL intake of sugar-sweetened beverages.

      Although I am not showing that comparison here, the ANNUAL increase in the percentage of obese adults (orange curve here) has a high resemblance to the ANNUAL SSB intake (the only curve here).

      Note I am not saying sugar-sweetened beverages are a main cause of obesity: what I am saying is that Guyenet’s argument is nonsense.

  4. Shameer Mulji

    What type of sugar is this referring to? Processed / industrialized sugar like table sugar, HFCS or all sugar including fruit, roots, tubers? Steffan Lindberg’s study on the Kitavans showed that they ate 70% of their calories from carbs (primarily starches and some fruit) but didn’t show any of the western diseases that we see today?

    Just asking for clarification. Thanks.

  5. Vicente

    By focusing on the straw man of the 1980 guidelines, Dr. Guyenet fails to address that question. That he’s taking on a straw man makes me thinks he’s more interested in appearing to win an argument than in dealing with what may be the single most important public health issue of our era.

    We can use a similar chart from the lung cancer/cigarette experience to further demonstrate the problem with Dr. Guyenet’s simplistic assumption that every cause has to be promptly and linearly associated with its effect.

    Gary Taubes

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