Does being overweight increase the risk of prostate cancer?

Being overweight is generally accepted to not be a healthy situation, but will being over-weight increase the risk of prostate cancer? Bodyweight is typically assessed in the US by calculating body mass index or BMI, which is your weight in kilograms divided by your height in meters squared. It is important to note that this equation does not measure body fat and it is excess body fat that increases disease risk, not excess muscle or bone weight that would increase your BMI as they would increase your body weight, but not your health risk.

Studies that assess large groups of men indicate that while obesity, as measured by BMI, does not seem to increase the risk of being diagnosed with prostate cancer, it does seem to increase the risk of dying from prostate cancer and also increases the risk of overall death after pros-tate cancer diagnosis.^{1 2 3} Being obese before prostate cancer diagnosis or after diagnosis has also been related to greatly increases the risk of cardiovascular disease death. ³ While overall excess body weight as measured by BMI does not seem to increase the risk of being diagnosed with prostate cancer, a large waist circumference can increase risk.¹ Waist circumference is used to indirectly measure abdominal obesity, which can indicate how much interior or visceral fat a person has. A waist that is more than 40 inches (102 cm) for a male is considered unhealthy.

A study of more than 16,000 US men looked at the relationship of BMI to prostate cancer risk with and without including waist circumference and found that while obesity (BMI > 30.0 kg/m2) was not related to prostate cancer risk, abdominal obesity (waist greater than 40 inches) with a BMI less than 30.0 kg/m2 (i.e., not categorized as obese) was associated with significant increase in the odds of prostate cancer diagnosis.¹ This provides evidence that where you store your fat is more important than the amount of overall fat you have on your body.

Thus, there is evidence to suggest that having excess body fat, and primarily fat at your waist, at the time of diagnosis of prostate cancer can mean a poorer prognosis. But, will losing weight help? There is some evidence that weight loss will help with outcomes. A study of men who were overweight or obese at the time of prostate cancer diagnosis randomly as-signed the men to weight loss (intervention group) or standard counseling that did not in-clude weight loss.⁴ The intervention group lost on average 5.5% of their baseline weight over a four to 16-week period which resulted in losses of body fat and visceral fat and a decrease in waist circumference. They also improved a number of labs that would be related to better prognosis and improved their quality of life.

Summary:

• Being overweight may not increase your risk of prostate cancer, but it could impact your risk of survival.
• Having too much fat at your waist is more of a health risk than overall excess body fat.