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Exercise and cancer: linkages with obesity?
1School of Physical & Health Education, Toronto, Ontario, Canada.
Summary
Physical activity, including hard work and active leisure, may lower cancer risk, particularly for colon tumors. Mechanisms may involve faster colonic transit and reduced body fat.
Area of Science:
- Oncology
- Epidemiology
- Physical Activity Research
Background:
- Growing evidence suggests a link between physical activity and reduced cancer incidence.
- Physical activity encompasses both occupational (hard work) and leisure-time pursuits.
- Cancer risk reduction is observed across various tumor types, with notable effects on colonic tumors.
Purpose of the Study:
- To synthesize findings on the relationship between physical activity and cancer incidence.
- To explore potential biological mechanisms underlying the observed protective effects.
- To differentiate the impact of different types and intensities of physical activity.
Main Methods:
- Review of well-controlled epidemiological studies.
- Statistical analysis controlling for confounding factors like body mass index.
- Exploration of proposed biological pathways, including gastrointestinal transit and hormonal regulation.
Main Results:
- Significant reduction in overall cancer incidence associated with physical activity.
- Strongest evidence for protection against colonic tumors, persisting after adjustment for BMI.
- Potential mechanisms include accelerated colonic transit time.
- Some evidence suggests protection against breast and reproductive tract tumors.
- Hormonal modulation and reduced body fat are proposed mechanisms for non-colonic tumors.
Conclusions:
- Physical activity is a significant factor in cancer risk reduction.
- Accelerated colonic transit is a likely mechanism for protection against colon cancer.
- Reduced body fat and modulated hormone secretion may contribute to protection against other cancer types.
- Further research into specific mechanisms and optimal activity levels is warranted.