Sugar-Sweetened Beverages: Strong Conjecture, Weak Evidence

We have ample reasons to eliminate sugar-sweetened beverages from our diets. The notion of policy initiatives to encourage people to do this attracts a lot of support, with good reasons. And yet, when we seek hard evidence for the effect that these initiatives will have on obesity, the evidence for a meaningful effect turns out to be weak.

David Allison and colleagues from the School of Public Health of the University of Alabama at Birmingham have just published an updated meta-analysis  in Obesity Reviews that makes a compelling case for that conclusion.

The point here is that obesity is a complex problem. We have lots of reasons to believe that sugar-sweetened beverages played a role in getting the prevalence of obesity up to an unacceptable level. But many other factors are also playing a role and we simply don’t know enough to make sweeping conclusions about precisely why we got here and what it will take to get us out of this mess.

Conviction is not enough, but it often carries the day. What we do need is a much larger body of real evidence: evidence for the mechanisms that drive obesity and evidence for interventions that will provide successful treatment and prevention.

It’s understandable that policy makers are unwilling to wait for definitive evidence before testing policies that might blunt the problem of obesity. But when we pretend to know more than we do, bias infiltrates research into the effect of policies we test, and the state of our knowledge stands still.

And it hardly helps to have beverage companies pretending that all calories count equally in contributing to obesity or that they can help solve the problem by exhorting people to get out and exercise. These two centerpieces of industry propaganda do nothing to foster dialog. They just engender mistrust.

What we need to confront the problem is honesty. We need honesty about the limits of what we know. And we need honest, probative research to expand the base of that knowledge.

Click here to read the meta-analysis in Obesity Reviews and here to read about the debate at Obesity 2012 that sparked this publication.

With a Twist of Orange, photograph © Jonathan Cohen / flickr

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