Sugar: Solve for the Answer You Like

The assumption that too much sugar explains our problem with obesity has become ambient white noise. Most people just accept it. Inconvenient facts fade into oblivion. Modelers grab the megaphone claiming to have evidence that sugar is the cause and the key for overcoming obesity. It’s easy enough to solve for the answer you like with a modeling exercise.

A shining example popped up last week in Economics and Human Biology. Alexander Bentley, Damian Ruck, and Hillary Fouts are offering up a model to show that sharp rises in obesity after 1990 are due to sugar calories consumed by children in the 1970s and 1980s.

Inconvenient Facts

Bentley’s model provides a tidy explanation for some inconvenient facts. A few years ago, Stephan Guyenet pointed out that obesity prevalence keeps rising despite recent declines in sugar consumption in the U.S.

Likewise in Australia, Jennie Brand-Miller and Alan Barclay documented declines in added sugar consumption. Likewise, they found declines in sugar from beverages. They studied time spans as long as 30 years. All the while, obesity was rising in Australia.

Given these inconvenient data, the new model by Bentley, Ruck, and Fouts seems quite ingenious. For U.S. data, they’ve found a time period where sugar consumption was rising. Then they’ve correlated it with a later rise in obesity prevalence. Correlation isn’t causation, but if you repeat the claim often enough, people will stop asking pesky questions. Besides, who would dispute the fact that too much sugar is surely a bad thing?

Narrow Thinking About a Broad Problem

The ultimate problem is this. Looking for a singular villain behind the excess of obesity is an exercise in self-deception. This problem comes from complex systems working together. We have a food supply that has more problems than a mere excess of sugar. Ultra-processed and calorie dense foods are everywhere we turn. As Kevin Hall and colleagues recently demonstrated, two different diets can have exactly the same sugar, salt, and fat content, but have very different effects on body weight.

And the problem of excess obesity goes far beyond food systems. Technology and our physical environment give us daily routines with less movement. Stress, distress, drugs, and chemicals contribute, too. The list of suspects is quite long. Thus, a model constructed to show that sugar is “sufficient to explain” 30 years of rising obesity is deceptive.

Confirmation Bias

Modeling can be an excellent tool for generating theories. But if you simply solve for the answer you like, what you get is confirmation bias. Such bias lends support to simplistic policies that – by themselves – will likely have no impact on obesity prevalence. And that would be a shame.

Click here for the modeling study and here for reporting on it.

Answers Carved in Stone, photograph © Eric Allix Rogers / flickr
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September 29, 2019