Dr. Rachel Ballard-Barbash, associate director of the Applied Research Program in the NCI Division of Cancer Control and Population Sciences, is helping lead NCI's new "energy balance" initiative. She has directed her related research efforts at expanding the evidence on the effect of diet, physical activity, and weight on cancer outcomes and at evaluating the factors influencing the adoption of recommended health behaviors in these areas.

Is there enough information on exercise and cancer risk to start applying that information clinically?
Clinical trials have not been done to test what specific types of exercise will reduce cancer risk or improve the prognosis of those with cancer. But there is sufficient evidence to suggest that exercise is likely to be beneficial for cancer. In addition, there is extensive evidence on exercise's benefits for other disease end points, such as heart disease or diabetes. The general health recommendations for regular activity apply to everyone, including people at high risk for cancer or those living with cancer. We can now say that, in addition to the evidence of a benefit for health problems such as high blood pressure and heart disease, there is some evidence that exercise can improve cancer outcomes.

What kind of activity appears to confer the most benefit?
Unlike with some other disease end points, we don't have specific information on what types of exercise are more beneficial for different cancers. For example, we know that aerobic exercise has a proven benefit for reducing heart disease risk. And weight-bearing exercise, particularly strength training, has proven to be very beneficial for osteoporosis. But for cancer, we don't yet have those kinds of specific data. One of NCI's efforts now is to inform the public and health community of the beneficial connection between exercise and cancer outcomes.

There are hypotheses about how exercise may confer a cancer benefit, but are any studies attempting to identify specific mechanisms?
A number of researchers - both basic and clinical - are initiating research to identify mechanisms. For example, in the NCI Center for Cancer Research, the Laboratory of Biosystems and Cancer is conducting research using animal models to delineate the mechanisms and investigate the interaction between exercise and chemoprevention agents. Work is also being done in the extramural community. Dr. Anne McTiernan at Fred Hutchinson Cancer Research Center, for instance, is conducting clinical studies focused on how specific exercise interventions affect mechanisms, such as alterations in estrogen and insulin metabolism, that influence cancer outcomes.