A prospective study of 78,500 men and women, ages 40-79, used wrist accelerometers to see whether daily step counts and measurements of intensity would predict future heart attacks or cancers (JAMA Intern Med, September 12, 2022). They were followed for an average of seven years, and during that period, there were 10,245 heart attacks, 664 deaths from heart attacks, 2813 cancers and 1325 deaths from cancer.
• Taking more steps each day (up to 10,000) was associated with reduced rates of cancer and heart attacks, and of deaths from these conditions.
• Intensity of walking (steps per minute) was an even better predictor of heart attacks and cancers than the total number of steps per day.

Previous studies have shown that taking more steps per day reduced risk for death from heart attacks (Int J Cardiol, 2019;278:267-272; J Am Heart Assoc, 2017;6(12):e007215; Int J Behav Nutr Phys Act, 2020;17(1):84) and many types of cancers (J Sport Health Sci, 2021;S2095-2546(21)00052-1; JAMA Intern Med, 2016;176(6):816-825).

Exercise Reduces Cancer Risk, Probably by Reducing Inflammation
A review of almost 170 animal and human studies shows that regular exercise is associated with reduced cancer risk, particularly for the types of cancers that are believed to be brought on by unhealthful lifestyles, such as those of the breast, colon, prostate, lung and endometrium (J Nutr, 2002 Nov;132(11 Suppl):3456S-3464S). Exercise appears to help prevent cancers by reducing causes of inflammation: overweight, excess calorie intake, high blood sugar, high insulin and insulin-like growth factor-1, high estrogen, and overactive or suppressed immune function (Exerc Sport Sci Rev, 2015;43(3):134-142); and by reducing markers of an overactive immune system that are also necessary for cancer growth (interleukin-6, tumor necrosis factor-α, and monocyte chemoattractant protein 1). Exercise has been shown to reduce inflammation that causes mice to develop colon cancer (Int J Oncol, 2014; 45(2):861–8) and breast cancer (Cytokine, 2011; 55(2):274–9). Exercise reduces inflammation in humans to increase survival from colon cancer (Gut, 2006; 55(1):62–7), and is associated with reduced precancerous polyps in humans (BMC Res Notes, 2012; 5: 312).

More than 21 studies have shown that exercise reduces risk for lung cancer (Cancer Causes and Control, 2005; 16(4):389–397). At least 36 studies found an inconsistent association between exercise and prostate cancer (Archives of Internal Medicine, 2005; 165(9):1005–1010). Exercise increased survival rate in breast cancer (JAMA, 2005; 293(20):2479–2486) and colorectal cancer (Journal of Clinical Oncology, 2006; 24(22):3527–3534). Exercise was associated with reduced risk of colon cancer by 30 to 40 percent, and those who were most active gained the greatest protection (Sports Medicine, 2004; 34(4): 239–252). Women who exercised were 20 to 80 percent less likely to develop breast cancer (Cancer Epidemiol Biomarkers Prev, 2006; 15(1):57–64), and time spent sitting was associated with increased breast cancer risk (Breast Cancer Res Treat, 2011; 130(1):183–94).

My Recommendations
Keeping on moving helps to prevent heart attacks and the cancers that are associated with an unhealthful lifestyle, such as cancers of the breast, colon, prostate, lung and inner lining of the uterus. If you do not exercise, I recommend starting an exercise program that will also help to protect you from obesity, diabetes and heart attacks. See How to Start an Exercise Program.

Caution: Be aware that exercise can cause heart attacks in people who already have blocked arteries. Check with your doctor, partcularly if you have any markers for arteriosclerosis: high blood pressure, cholesterol or blood sugar, or being able to pinch more than three inches of fat over your belly. See Heart Attacks and Cancers Share the Same Risk Factors