Six Hard Questions to Ask About Obesity Cause and Effect

Yesterday, Kevin Fontaine and David Allison opened their third conference on causality in obesity research at the UAB Nutrition and Obesity Research Center. They explained the growing urgency to ask hard questions about cause and effect in obesity.

Targeting Elusive Causes for Obesity

For three decades, obesity prevalence has been growing relentlessly. And yet, we do not know exactly why. Plenty of ideas come forward to explain it. And some become articles of faith. Through the 1980s and 1990s, high-fat foods were prime suspects. And yet policies to promote lower-fat diets appeared to make the problem worse.

As a result, attention has shifted to sugar. Policymakers now regard added sugars in processed foods as especially bad actors. So consumers are growing wary of them and nutrition facts labels will soon call them out. Soda taxes are gaining traction in many places to target added sugar.

Many other causes – e.g. food deserts, restaurant food, built environments – receive attention for contributing to obesity. But efforts to reduce their presumed impact have yielded little success.

Allison and Fontaine acknowledge progress in understanding obesity – its physiology, genetics, neuroscience, measurement, stigma, and more. But progress on interventions has been more modest. Despite advances on behavioral, drug, and surgical therapies, the current options leave much to be desired.

Population-health strategies have not yet been adequate to reverse the continuing rise in obesity’s impact on health.

Asking Hard Questions

Considering all this, we need to ask hard questions about what we think we know about obesity.

1. How can we know that? For instance, how can we be more confident of dietary factors that contribute to obesity. Presumptions and logic are not good enough.

2. What else could explain this? Reverse causality is just one explanation frequently overlooked.

3. Does the study test it? Without an adequate design, we cannot know if a cause and effect relationship truly exists. Associations are mere starting points.

4. What’s the mechanism? If we cannot explain how a presumed effect might result from an action or an exposure, causality remains a assumption. Not a fact.

5. Can we measure it? Without robust methods, we cannot provide reliable results. Measuring dietary intake in the real world is one such challenge.

6. Did we measure the real outcome? Surrogate measures are convenient, but useless if not validated. Many of the outcomes for soda taxes are tied only to soda consumption. Overall dietary patterns are tougher to measure. But the real outcome to watch is the impact on obesity prevalence. We have nothing on that yet, except for high hopes.

Children have great skills for asking hard, but simple questions. Perhaps we can remember to do the same.

For more information on this year’s conference, along with the full video proceedings of the first two, click here.

Any Questions? Photograph © Matthias Ripp / flickr

Subscribe by email to follow the accumulating evidence and observations that shape our view of health, obesity, and policy.

July 25, 2017