How is BMI Associated with Prostate Cancer Risk?
— By Dawn M. Sweet, Ph.D
Lifestyle changes may reduce the risk of prostate cancer in men.
There is evidence to suggest that men with obesity may be at a greater risk of developing prostate cancer than healthy-weight counterparts.1 Prostate cancer is the second most common cancer reported in men and it is the fifth leading cause of death worldwide2, accounting for approximately 3.8 percent of cancer-related deaths in men.3
Given the incidence of prostate cancer, it is important to understand how BMI is associated with prostate cancer risk and the impact of exercise on prostate cancer.
Prostate Cancer and BMI
According to a 2021 review4 of over nine million men, including 191,000 men with prostate cancer, an eight to 11 percent increase in prostate cancer risk was observed in men with obesity. Similar results were supported in other meta-analyses that found a six percent increase for every 5 kg/m2 increase in BMI5 while another meta-analysis found a nine percent increase in prostate cancer mortality with every 5 kg/m2 increase in BMI.6 Recurrence of cancer is also more likely in men with obesity. In a retrospective cohort study7 that included 1,337 men, an age-adjusted model showed a two-fold increase in prostate recurrence risk for men with obesity.
Physical Activity and Prostate Cancer
Exercise can reduce the risk of prostate cancer in men with obesity. In a study that included 2,705 men over 18 years, vigorous physical activity was associated with a lower risk of PCa mortality.8 Each physical activity — e.g., jogging, walking, weight training, etc. — was assigned a metabolic equivalent task (MET), which measured energy expenditure relative to time compared to being at rest (e.g., sitting). An activity was classified as non-vigorous if its MET value was ≥ 6. It should be noted that exercise levels were self-reported and limited to a predetermined subset of activities that included walking, heavy outdoor work, cycling, tennis and other racquet sports, calisthenics (e.g., rowing), weightlifting, running or jogging, and swimming laps.
Walking was the most often reported activity, with a total of 36 percent MET hours per week and 52.4 percent of total activity time per week. Heavy outdoor work (21.6 percent of MET hours; 19.2 percent of total time) and bicycling (10 percent of MET hours and 7 percent of total time) were also significant contributors. Men who achieved a MET of ≥ 9-h/week reduced their chance of all-cause mortality by 33 percent and PCa-specific death by 35 percent after controlling for other risk factors. The data support physical activity to mitigate the risk of death by prostate cancer.
Because increased physical activity leads to weight loss, the progression of cancer and decrease in risk could be attributed to increased insulin sensitivity which could affect insulin growth factor (IGF) axis. It’s suggested that men who exercise following a prostate cancer diagnosis might be benefitting from lower serum insulin and IGF-1 and higher IGF binding protein-1. Physical activity is also associated with reduced inflammatory factors and increases in anti-inflammatory cytokines, thus inhibiting proinflammatory cytokine production. Finally, exercise is positively correlated with immune system health, so men with prostate cancer who follow an exercise program could benefit from an exercised-induced boost to their immune systems.8
Exercise, Diet and Meal Replacements
A BMI in an unhealthy range can increase men’s risk of prostate cancer. To mitigate risk, men should be encouraged to follow an exercise program following diagnosis, when medically cleared to do so. Complementing an exercise program with a healthy eating plan, such as a Low Calorie Diet (LCD) or a Very Low Calorie Diet (VLCD) with nutritionally formulated meal replacements, can help men with prostate cancer ensure they are getting the necessary vitamins and minerals needed to participate in an exercise program. Vigorous physical activity was associated with reduced PCa-specific mortality, so health care professionals should consider working with patients to develop a vigorous exercise program that they can safely pursue. Non-vigorous exercise also has benefits, so for patients who may not be strong enough to follow a vigorous exercise program, a non-vigorous program should be developed.
7 Weight gain is associated with an increased risk of prostate cancer recurrence after prostatectomy in the PSA era 8 Physical activity and survival after prostate cancer diagnosis in the health professionals follow-up study