No increase in serious injuries occurred from physical
activity or unintended adverse changes in dietary
intake, on the basis of available counseling trials (Table
3). Two trials reported a paradoxical increase in carbohydrate
intake but not overall caloric intake. The clinical
significance of these dietary changes is unclear. In
the Women’s Health Initiative, the replacement of fat
intake with complex carbohydrates over 6 years was not
associated with adverse effects on lipid profiles (139).
Observational studies suggest an increased risk for serious
cardiac events during vigorous physical activity, primarily
in persons with low levels of habitual activity.
However, the absolute risk for serious cardiac events
related to physical activity seems very small. The U.S.
Department of Health and Human Services’ 2008 report
on physical activity (6) details additional information
regarding harms of physical activity.