Physical activity is a complex, multidimensional behavior, the precise measurement of which is
challenging in free-living individuals. Nonetheless, representative survey data show that 35% of the
European adult population is physically inactive. Inadequate levels of physical activity are disconcerting
given substantial epidemiologic evidence showing that physical activity is associated with decreased
risks of colon, endometrial, and breast cancers. For example, insufficient physical activity levels are
thought to cause 9% of breast cancer cases and 10% of colon cancer cases in Europe. By comparison, the
evidence for a beneficial effect of physical activity is less consistent for cancers of the lung, pancreas,
ovary, prostate, kidney, and stomach. The biologic pathways underlying the association between
physical activity and cancer risk are incompletely defined, but potential etiologic pathways include
insulin resistance, growth factors, adipocytokines, steroid hormones, and immune function. In recent
years, sedentary behavior has emerged as a potential independent determinant of cancer risk. In cancer
survivors, physical activity has shown positive effects on body composition, physical fitness, quality of
life, anxiety, and self-esteem. Physical activity may also carry benefits regarding cancer survival, but
more evidence linking increased physical activity to prolonged cancer survival is needed. Future studies
using new technologies – such as accelerometers and e-tools – will contribute to improved assessments
of physical activity. Such advancements in physical activity measurement will help clarify the
relationship between physical activity and cancer risk and survival. Taking the overall existing evidence
into account, the fourth edition of the European Code against Cancer recommends that people be
physically active in everyday life and limit the time spent sitting.