Physical Activity: 6 Ways to Define Truth

Physical activity is a subject that can stir up a civilized conflict among obesity researchers and the current issue of the International Journal of Epidemiology has done just that. With a provocative analysis of physical activity’s role in obesity, Amy Luke and Richard Cooper inspired five more commentaries from distinguished experts on the subject. Here’s a brief summary of the perspectives offered.

  1. Physical Activity Does Not Influence Obesity Risk. In this analysis that started the debate, Luke and Cooper conclude the evidence is not adequate either to prove that reduced physical activity is responsible for the growth in obesity rate or to prove that increased physical activity could blunt the surge in obesity. Thus, they say, it’s “time to clarify the public health message.”
  2. Wrong: Physical Activity Has a Crucial Role. Steven N Blair, Edward Archer, and Gregory Hand are especially blunt in refuting Luke and Cooper. They cite a large body of evidence that physical activity has contributed to the obesity epidemic and unequivocal evidence that it has an important role in weight management.
  3. Physical Activity Is a Minor Player. Boyd Swinburn essentially accepts that physical activity has played a minor role in the obesity epidemic and moves on to a wide-ranging exploration of ambitious approaches to reversing the epidemic.
  4. Food and Physical Activity Both Affect Body Weight. James Hill and John Peters characterize Luke and Cooper’s analysis as unbalanced and incomplete. They conclude by suggesting that the paper offers more sensationalism than science and wondering if the paper “was reviewed by anyone with expertise in exercise science.”
  5. The Relationship Is Complex and Uncertain. Nicholas Wareham and Soren Brage focus their criticism on Luke and Cooper’s call to change public health messages related to physical activity. They “argue for caution when considering altering public health messages as the risks for confusion of the public are considerable.”
  6. Sufficient Physical Activity Does Influence Obesity Risk. Gordon Fisher, Gary Hunter, and David Allison go right to the specifics of what the research has shown the effects of physical activity on obesity to be. They describe in detail what is required for physical activity to be effective and gaps in studies that can lead to a false conclusion of no effect.

Given the last word, Luke and Cooper were taken aback by the controversy they stirred up, saying:

It was naïve of us not to realize ahead of time that the tone of our comments would be objectionable to some of our colleagues who have spent their careers as researchers and champions of physical activity, and have made hugely important contributions to both the science and to public health.

Perhaps the debate serves some useful purposes. It defines the limits of what we know about physical activity and obesity. It clarifies what we really do know. And it brings a focus to the considerable challenge of translating research into meaningful health messages.

Make no mistake. Physical activity offers important health benefits and has important effects on obesity. Maintaining a healthy weight is tough unless you’re physically active.

Click on each of the summaries above to access the articles published in this debate of physical activity and obesity

Marbled Godwits in a Brawl, photograph © AdititheStargazer / flickr

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