Body Mass Index (BMI) is a tool for indicating weight status in adults. To calculate yours electronically, visit www.nhlbi.nih.gov and search for "BMI Calculator."
A critical balance
Not only are most Americans too heavy, they're also too sedentary. Weight and physical activity are intimately related as two sides of the "energy balance" of the body, and they both contribute to the cancer equation. Keeping weight down and activity up not only lessen a person's chance of developing cancer to begin with, but also can improve his/her outcome if the disease occurs.
For example, Dana-Farber researchers Jeffrey Meyerhardt, MD, and Charles Fuchs, MD, found that patients who underwent surgery for Stage III colon cancer were less likely to have a recurrence if they exercised regularly. The regimen wasn't overly strenuous: It was the equivalent of walking an hour a day six times a week or jogging three to four hours a week. "This shows there are things that colon cancer survivors can do, in addition to chemotherapy, to reduce the likelihood that the disease will come back," says Meyerhardt.
Obesity's role in colon cancer recurrence risk isn't yet clear, but research suggests that weight gain following diagnosis raises the risk of recurrence after treatment and worsens survival odds. Malcolm Robinson, MD, of Brigham and Women's Hospital and Jennifer Ligibel, MD, in the Women's Cancers Program of Dana-Farber/ Brigham and Women's Cancer Center are testing exercise regimens and weight control for their potential to lower certain hormones, including insulin, whose levels are higher in overweight women and may raise the likelihood of breast cancer returning.
While obesity clearly is an important culprit in both overall cancer risk and many individual malignancies, the picture is complicated. Overweight women are actually at lower risk of breast cancer before menopause. After menstruation stops, however, the risk for obese women rises above that of their normal- weight counterparts—but only in those who don't take hormone replacement therapy. The jury is still out in ovarian and prostate cancer; some studies have found an obesity link, while others have not.
What must not be lost, cautions Benz, is compassion for individuals who struggle to control their weight; after all, many people have a higher bar to reach because of a genetic predisposition. "I feel there's too much blaming of patients for obesity," he says. "If these associations with cancer hold true, we must be sure we don't have another group of patients who carry a stigma."
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