Inflated Promises of Exercise for Fitness and a Longer Life
To be sure, exercise has many benefits – including the widely accepted benefit of fitness and a longer life. But a new study of causal inference linking fitness to reduced mortality suggests those benefits have been exaggerated.
The problem is an old one: Confounding. The senior author of the new study, Marcel Ballin, explains:
“We found that people with high fitness levels in late adolescence had a lower risk of dying prematurely, for example from cardiovascular disease, compared to those with low fitness levels. But when we looked at their risk of dying in random accidents, we found an almost similarly strong association. This suggests that people with high and low fitness levels may differ in other important ways, which is something that previous studies have not fully taken into account.”
Other Factors in Play
In the simplest terms possible, other factors seem to work in the background. Those other factors help men with high fitness in their late teens live longer. Very fit individuals had about half the risk of death over four decades of follow-up. But negative control outcomes and sibling comparisons in this analysis point to reasons other than fitness for at least some of the reduction in mortality. The authors conclude:
“This suggests that fitness levels and mortality risk are influenced by strong socioeconomic, genetic, and behavioural confounding factors that differ between more fit and less fit people. Indeed, there is a well-known social gradient in both fitness and major somatic diseases (e.g. cardiovascular disease), as well as a clear contribution of genetic predisposition.”
Why Does It Matter?
Why should we care? This is a perfectly reasonable question. But the answer is really quite simple. Exaggerating the promise of exercise for a fitness and a longer life can lead people to make bad choices. At a policy level, we see decisions based on an assumption that fitness might solve big problems all by itself. Individuals might neglect other choices that are equally important.
Big promises can lead to big disappointments and then disillusionment. Realistic expectations set the stage for success.
Click here for the study and here for further perspective.
Stěhovaci Kabinet (Moving Cabinet), collage by Jindrich Styrsky / WikiArt
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May 30, 2025
