Claude Bouchard and colleagues have looked at six studies of physical activity and found that exercise actually made cardiometabolic risk factors worse for many subjects. The prevalence of adverse events for select risk factors was 8.3% for exercise training induced changes in fasting insulin, 10.4% for triglycerides, 12.2% for systolic blood pressure, and 13.3% for changes in high-density lipoprotein cholesterol (the good cholesterol). 7% of subjects had adverse increases in two or more cardiometabolic risk factors.
The six studies provided data on 1,687 adults. Adverse events were defined to exclude within-subject deviations over a given period of time. To establish this, the researchers studied 60 subjects who were measured three times over three weeks for each trait. This produced what they refer to as the technical error or TE. An adverse event was defined as 2 times the TE in a direction indicating a worsening of the risk factor. The risk factors measured were systolic blood pressure, triglycerides, fasting insulin, or decrease in HDL-C. PLOSOne: Adverse Metabolic Reaction to Exercise
The implications of this study are enormous. First, it appears on the front page of today’s New York Times, NYT:Kolata: Can exercise be bad for you, so it will get wide publicity. Second, it will spur more research on other cardiometabolic risk factors and exercise. But also, the paper points out that the response pattern to exercise aggregates in families. In fact, the authors point out, “the genetic component of a response trait can be defined in terms of RNA abundance observed in the sedentary state or by specific genomic variants. This suggests that it may be possible with further research to identify molecular predictors of the inability to benefit from regular exercise and of adverse changes in specific cardiometabolic and diabetes risk factors.
Third, the study is bound to have an impact on national recommendations for universal levels of physical activity. The one-size-fits-all recommendations must now take into account the adverse effects to a significant part of the population.
Finally, this is likely to throw the drug/device approval process at the Food and Drug Administration into some turmoil. Particularly with drugs, their safety and effectiveness is compared to a placebo group which is receiving a diet and exercise intervention. If some in the placebo group are showing a worsening of the cardiometabolic risk factors, it would make the drug look less effective. But overall, it raises the question, “If exercise were a drug, would the FDA approve it for treating obesity?” Given the current environment, the answer is clearly no. Thus, were the FDA to address this question they would at variance with the Institute of Medicine, most physicians, the CDC, HHS and, oh yes, Michelle Obama.