Higher Body Mass May Cut Prostate Cancer Risk

Researchers at the Harvard School of Public Health have found that in certain cases, stouter men are at a decreased risk of developing prostate cancer.

The study, published recently in the Journal of the National Cancer Institute, found that men with a higher Body Mass Index (BMI)—calculated by dividing a person’s weight in kilograms by height in meters squared—are at less risk for hereditary prostate cancer than men with a lower BMI.

Prostate cancers are classified as hereditary when they strike men younger than 60 years old or with a family history of the disease.

For sporadic prostate cancer, seen in men older than 60 or without a family history, the link between BMI and cancer risk was weak and not statistically significant.

A high BMI “has been associated with a higher risk of many cancers, but the studies have not been so consistent for prostate cancer,” said Associate Professor of Medicine Edward L. Giovannucci ’80, the study’s lead author.

To clarify this inconsistency, the researchers used data from the Health Professionals Follow-Up Study—which documented 2,896 reported cases of prostate cancer from February 1, 1986 to January 31, 2000—to probe links between girth and prostate cancer.

“By understanding the causes of prostate cancer better, we hope to eventually be able to offer more in terms of prevention,” Giovannucci said.

He hypothesized that “it is possible that prostate cancers that tend to occur in older men have another cause unrelated to obesity,” but said he was unsure of a solid explanation for the results.

In the report, the researchers wrote that because “obesity is associated with lower circulating concentrations of testosterone,” the results might point to the more direct role of androgens in risks for early-onset or hereditary prostate cancers than in sporadic prostate cancers.

“It has been shown in other studies that obesity in men is related to lower androgens levels so we hypothesize that this may account for the relationship we’ve observed,” Giovannucci said. “We need to do more studies in which we directly measure androgens levels in men, along with BMI, and assess simultaneously their association with prostate cancer.”