We all know that maintaining a healthy weight; eating a healthful, balanced diet; and exercising regularly are good for our health. But did you know that your weight, what you eat, and how much you exercise can influence your risk for certain types of cancer? For decades, the American Cancer Society has supported pioneering research to find answers to determine how body weight, diet, and exercise affect cancer risk, and our relentless pursuit of those answers continues today. Recent Society-supported research has shed new light on the relationship between excess weight, diet, exercise, and cancer risk.
How Do Diet and Exercise Affect Cancer Risk?
To determine how following Society nutrition and physical activity guidelines affects death rates from cancer, Marji McCullough, ScD, RD, a Society epidemiologist, examined data on 112,000 nonsmoking men and women who had participated in the American Cancer Society Cancer Prevention Study II. She found that individuals who adhered closely to the Society’s nutrition and physical activity guidelines reduced their risk of dying of cancer by 25% to 30%.
A diet high in red meat is a known risk factor for colon and other cancers, most likely because of cancer-causing substances called carcinogens that are generated when red meat is cooked at high temperatures. These carcinogens damage cellular DNA. With Society funding, researcher Marian Stern, PhD, studied these DNA changes and found that certain individuals may be particularly susceptible to DNA damage from eating red meat. Her research may lead to ways to identify people at high risk so they can take steps to reduce their cancer risk.
New findings from Society researcher Alpa Patel, PhD, suggest that reducing the risk of cancer and heart disease is more than a matter of how much you exercise. Dr. Patel studied data on 123,000 participants in the American Cancer Society Cancer Prevention Study II who had no history of cancer, heart attack, stroke, or lung disease. She found a strong relationship between the amount of leisure time spent sitting and the risk of death, especially in women, that was independent of levels of physical activity. Women who reported more than six hours per day of sitting were 37% more likely to die during the time period studied than those who sat fewer than three hours a day.
A number of investigators have hypothesized that exercise might help patients cope with the rigors of cancer treatment. In a series of related studies, Society grantee Reid Hayward, PhD, reported that cancer patients who followed a moderate-intensity, individualized exercise program after cancer therapy maintained or improved cardiovascular and pulmonary function while also reducing cancer-related fatigue and depression.
Uncovering the Link between Body Weight and Cancer
Society researchers were among the first to identify the relationship between excess body weight and cancer. In 2003, Society epidemiologist Eugenia Calle, PhD, studied more than 900,000 men and women and found that the risk of cancer death was 1½ times higher in overweight men than in men of normal weight and even higher in overweight women compared with normal-weight women.
New Society research has demonstrated a link between waistline and risk of cancer death. Eric J. Jacobs, PhD, found that men and women with very large waists – 47 inches or larger in men and 42 inches or larger in women – have twice the risk of death from cancer, heart disease, and respiratory disease compared with those with the smallest waists – 35 inches or smaller in men and 30 inches or smaller in women. This holds true even for men and women who were not overweight. So inches may be as important as pounds.
Understanding How to Help People Make Healthier Choices
Society-funded researcher Tom Baranowski, PhD, has endeavored to identify approaches that encourage long-term increases in the consumption of fruits and vegetables. In one of his studies, Dr. Baranowski designed an intervention that awarded a special badge to Boy Scouts who adopted healthier eating habits. The study showed that participants adopted a diet higher in fruit juice and low-fat vegetables immediately after the intervention, but that the diet was not maintained six months later. This study shows that behavior change is possible, but underscores the need for alternative strategies to sustain long-term changes in diet.
Childhood survivors of acute lymphoblastic leukemia (ALL) are at increased risk for obesity, which could increase their risk of a new cancer later in life. Society-funded researcher Jeannie Huang, MD, MPH, and her colleagues are addressing the unique medical and psychosocial needs of these individuals by developing a tailored weight-loss program to overcome the physical restrictions, weight-management issues, and negative body image faced by adolescents who have survived childhood ALL. The intervention, which is being delivered using text messaging, phone counseling, and the Internet, is being evaluated in a randomized controlled clinical trial to test its effects on weight loss, sedentary behavior, and quality of life.