Physical activity, obesity and sedentary behavior in cancer etiology: epidemiologic evidence and biologic mechanisms

• Published in: Molecular oncology Vol. 15; no. 3; pp. 790 - 800
• Main Authors: Friedenreich, Christine M., Ryder‐Burbidge, Charlotte, McNeil, Jessica
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.03.2021; John Wiley and Sons Inc; Wiley
• Subjects: Amyloid; Animals; Behavior; Body mass index; Body weight gain; Breast cancer; chronic inflammation; Colon; Cytokines; Disease prevention; Energy expenditure; Energy intake; Energy requirements; Epidemiology; Esophagus; Etiology; Exercise; Globulins; Growth factors; hormone; Humans; Incidence; Insulin; Insulin-like growth factors; Lung cancer; Medical research; Metabolism; Neoplasms - epidemiology; Obesity; Obesity - complications; Ovaries; Physical activity; Physical fitness; Prostate; Protective Factors; Reactive oxygen species; Review; Risk Factors; Sedentary Behavior; Sex hormones; Smoking; Tumor necrosis factor; Tumor necrosis factor-TNF; metabolism; sedentary behavior; chronic inflammation; obesity; hormone; physical activity
• ISSN: 1574-7891; 1878-0261; 1878-0261
• DOI: 10.1002/1878-0261.12772

An estimated 4 in 10 cancers are preventable through modifiable risk factors. This review summarizes the epidemiologic evidence linking physical activity, sedentary behavior, and obesity with cancer risk. We explore the possible biologic mechanisms underpinning the associations between these lifestyle factors and cancer incidence, including effects on endogenous sex steroids and metabolic hormones, insulin sensitivity, and chronic inflammation. An estimated 30–40% of cancers can be prevented through changes in modifiable lifestyle and environmental risk factors known to be associated with cancer incidence. Despite this knowledge, there remains limited awareness that these associations exist. The purpose of this review article was to summarize the epidemiologic evidence concerning the contribution of physical activity, sedentary behavior, and obesity to cancer etiology and to provide an overview of the biologic mechanisms that may be operative between these factors and cancer incidence. Strong and consistent evidence exists that higher levels of physical activity reduce the risk of six different cancer sites (bladder, breast, colon, endometrial, esophageal adenocarcinoma, gastric cardia), whereas moderate evidence inversely associates physical activity with lung, ovarian, pancreatic and renal cancer, and limited evidence inversely correlates physical activity with prostate cancer. Sedentary behavior, independent of physical activity, has been shown to increase the risk of colon, endometrial, and lung cancers. Obesity is an established risk factor for 13 different cancer sites (endometrial, postmenopausal breast, colorectal, esophageal, renal/kidneys, meningioma, pancreatic, gastric cardia, liver, multiple myeloma, ovarian, gallbladder, and thyroid). The main biologic mechanisms whereby physical activity, sedentary behavior, and obesity are related to cancer incidence include an effect on endogenous sex steroids and metabolic hormones, insulin sensitivity, and chronic inflammation. Several emerging pathways related to oxidative stress, DNA methylation, telomere length, immune function, and gut microbiome are presented. Key recommendations for future research in both the epidemiology and biology of the associations between physical activity, sedentary behavior, obesity, and cancer risk are also provided.