Against Sugar: The Messenger and the Message

Many Americans have begun to turn against sugar. Gary Taubes has been leading the charge with his book The Case Against Sugar, which sharpens the attacks he made in his previous two books, Good Calories, Bad Calories and Why We Get Fat.

Gary Taubes has risen high enough that he is set up for a fall. And there is plenty of dirt. He has played fast and loose with some of his history, putting words in the mouth of long-dead scholars they said or meant, and pointing out that people he disagrees with were compromised by sugar-industry ties, but neglecting to point out that people he agrees with were compromised by other food-industry ties.

I sense some “how the might have fallen” glee in Megan Molteni’s June 18, 2018 Wired article “The Collapse of a $40 Million Nutrition Science Crusade.” It turns out that Gary Taubes has lost some of the money-raising magic he had back in 2011.

In telling a story of the messenger’s fall from grace, Megan goes too far in disparaging the anti-sugar message. The devil is in the details of two experiments that had benefitted from Gary Taubes’s fund raising. Here is Megan’s description of the first experiment:

The EBC’s pilot project would lock 17 overweight men inside metabolic wards for two months, feeding them precisely formulated meals and pricking and prodding to see what happened to their bodies on a low-carb diet. If it made them burn calories faster, a follow-up study would do the same tests on a bigger group of people. If the effect was minimal, researchers would then test the effect of low-carb diets on hunger.

In my view, of these two possible effects of a lowcarb diet, the effect on hunger, which they never got to, is by far the most interesting. If a lowcarb diet makes you less hungry, that could help a lot with weight loss in the real world. But in a metabolic ward study, the amount people are fed is the same whether they are hungry or not.

Another limitation of a metabolic ward study is that changes in physical activity that might result at home from a lowcarb diet making someone feel more energetic might not happen while cooped up in a metabolic ward.

Results for two other experiments that benefitted from Gary Taubes’s fund raising won’t come in until later on this year. But here is Megan’s description of the other experiment whose results are in:

The fourth and largest one, conducted at Stanford, randomized 600 overweight-to-obese subjects into low-fat versus low-carb diets for a year and looked at whether or not their weight loss could be explained by their metabolism or their DNA. Published this February in JAMA, the study found no differences between the two diets and no meaningful relationship between weight loss and insulin secretion.

Megan badly misreads what the study actually shows. Both diets told people to go off sugar, refined carbs, and processed food, and both looked like a big success in helping people lose weight. Hardly a failure for an anti-sugar message! (For more discussion, see “Why a Low-Insulin-Index Diet Isn’t Exactly a ‘Lowcarb’ Diet” on my blog.) What is more, the fact that a high-fat/lowcarb diet avoiding sugar, refined carbs and processed food was just as good as a lowfat diet avoiding sugar, refined carbs and processed food is a victory for the idea that dietary isn’t the evil it has long been made out to be.

To the disappointment of the researchers in the Stanford study, the two diets each seemed to work well with no hint of whom they would work best for. Trying to predict with DNA, they used an outdated “candidate gene” approach, focusing on only 3 gene indicators (SNPs). (Fortunately, they have the data to try again using a combination of many more genes.) They also couldn’t predict weight-loss success from an initial test of how strongly someone’s insulin levels spiked after taking in sugar. The inability to predict for whom a given diet would work best was a failure to replicate previous studies. (On replication failures, see my post "Let's Set Half a Percent as the Standard for Statistical Significance.")

A difficulty in predicting weight-loss success from a test of how strongly someone’s insulin levels spiked after taking in sugar tells less than it might sound. On the one hand, a strong insulin response might mean that cutting out sugar or other carbs could bring down insulin levels more. On the other hand, a strong insulin response might mean that the bad stuff people were still eating because they weren’t doing everything right might be likely to keep their insulin levels high enough that they had more trouble getting to an insulin level low enough for weight loss. Here, what complicates matters is that the relationship between insulin levels and weight loss may not be a straight line. There may be a big middle range where weight stays about even, with weight loss at quite low levels and weight gain at quite high levels. Right now, that is only a logical possibility. The research hasn’t been done to know.

In any case, the inability to predict how much weight someone would lose from how strongly their insulin levels reacted to taking in sugar is all there is in this study to back up Megan’s statement that there was “no meaningful relationship between weight loss and insulin secretion.” There is nothing beyond that in the study to question the idea that insulin is an important part of the mechanism for weight gain or weight loss.

The bottom line is that despite the clay feet of the messenger—the decline in Gary Taubes’s fund-raising prowess and his other flaws—the anti-sugar message is still looking strong.


Don't miss these other posts on diet and health and on fighting obesity:

Also see the last section of "Five Books That Have Changed My Life" and the podcast "Miles Kimball Explains to Tracy Alloway and Joe Weisenthal Why Losing Weight Is Like Defeating Inflation." If you want to know how I got interested in diet and health and fighting obesity and a little more about my own experience with weight gain and weight loss, see my post "A Barycentric Autobiography."