If you or a loved one has prostate cancer and is obese with a body mass index of 30 or higher, results from these two studies provide added incentive for shedding excess weight.

Prostate Cancer Study 1: Prostate cancer is more likely to spread in men who are obese at diagnosis, according to findings from a study reported in the journal Cancer (Volume 109, page 1192).

The researchers monitored the outcomes of 752 men with local- or regional-stage prostate cancer. The men ranged in age from 40-64. Sixteen percent were current smokers, 14% had tumors with a Gleason score of 7 or higher, 63% were treated with radical prostatectomy alone, and 72% had PSA levels of 4.0 ng/mL or higher when diagnosed.

After an average of nearly 10 years, obese men (body mass index of 30 or higher) were more than three times as likely to have developed metastases and were more than twice as likely to have died of prostate cancer than their nonobese counterparts.

These findings held true even after the researchers took into account factors that could have increased the likelihood of prostate cancer spread and death. The poorer outcomes in obese men may be related to alterations in sex hormones, increases in cancer-promoting substances like leptin, or high levels of inflammatory molecules, all of which are associated with excess body fat.

Prostate Cancer Study 2: Prostate cancer treated by radiation therapy is more likely to recur in men who are obese. That's the conclusion of researchers who assessed the outcomes of 706 men with localized prostate cancer treated with radiotherapy.

The study participants' average age at diagnosis was 72, and they were monitored for nearly eight years. Normal weight was defined as a body mass index (BMI) of less than 25; overweight, 25-29.9; and obese, 30 or higher. About 28% of the men were normal weight; slightly more than half were overweight, and about 22% were obese. The obese men had been diagnosed at a younger age than the nonobese men, but they were similar in terms of disease stage, pretreatment PSA level, and Gleason score. None had received androgen-deprivation therapy.

The results showed that the average time to biochemical recurrence (relapse of prostate cancer detected by a rising PSA level) was 93 months for normal-weight men, 88 months for overweight men, and 84 months for obese men. It's too early to say that losing weight can lower your risk of a relapse of prostate cancer if you're obese, but these results show that obesity is a major health concern that affects more than your heart. Data was reported in the British Journal of Urology International (Volume 100, page 315).