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Adverse Metabolic Effects of Exercise?

obesity-exerciseWarning – this is not an April Fool’s post! Rather, it is a follow up to yesterday’s post warning that even “lifestyle” or behavioural interventions can have adverse effects – at least for some people.

Point in case, is this paper by Claude Bouchard and colleagues, published in PLOS one back in 2008, clearly documenting clinically significant harmful metabolic effects of exercise in some individuals (about 1 in 10).

I would probably have disregarded this paper, except for the fact that the authors include a who-is-who of exercise experts, Steven Blair, Timothy Church, Nathan Jenkins, just to name a few. These are all enthusiastic supporters of increasing physical activity with rock-solid expertise in exercise physiology.

Their findings are based on completers from six exercise studies involving a total of 1,687 men and women.

Although metabolic parameters in general improved (as expected) in most participants, 8.4% had an adverse change in fasting insulin, 12.2% has a clinically significant increase in resting systolic blood pressure, 10.4% had a relevant increase in fasting triglycerides, and 13.3% had a reduction in HDL-Cholesterol. About 7% of participants experienced adverse responses in two or more risk factors.

While the authors note that the explanation for these findings remain unclear,

“…the adverse response traits are not explained by prior health status of subjects, age, amount of exercise imposed by the program, or lack of improvement in cardiorespiratory fitness. No evidence could be found for the hypothesis that adverse responses were the result of drug-exercise interactions.”

Which brings me back to yesterday’s post, that even the best meant behavioural recommendation (in this case “move more”) can carry risks for some individuals and may require personalised and ongoing monitoring.

Funnily enough, I would imagine that if you packed exercise into a pill with these types of “adverse effects”, I wonder if the FDA would actually let you sell it.

Incidentally, Claude Bouchard will be one of the key note speakers at the upcoming 4th Canadian Obesity Summit in Toronto, April 28-May 2. I’m sure he will be presenting some of these data and the fascinating genetic studies that have since been done on this issue.

Edmonton, AB

Hat tip to Morgan Downey for reminding me of this study.

To preregister for the Canadian Obesity Summit click here


  1. Studies suggest genetics plays an important role in how people respond to exercise. Here’s a couple of links:

    One size fits all exercise recommendations may need to be revisited. But as far as I’ve read, there is a genetic test (from XRGenomics) to predict your aerobic response to exercise, but not other metabolic factors (e.g. blood pressure, lipidemia, insulin resistance).

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  2. Dr Sharma i am not a medical professional but i am in the business of supporting people with obesity and obesity related conditions . I was so disappointed that i was not accepted to take the free online course you posted earlier this month. I encourage you to support those people in communities who are serving the general public as there are way more of me than medical professionals therapists and nurses .
    It is my passion to support people with the condition of obesity to live a happy and joy filled life fat or thin or just thinner . I know I am not the only one we need leadership and guidance and your the best of the best to do it

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  3. Perhaps the exercise regime was too stressful and 8.4% participants could not adapt properly.

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