Excess Body Fat Associated with Increased Risk for Six Cancers

WASHINGTON, Oct. 31 -- Obesity is on course to overtake tobacco as the leading risk factor for cancer in America, according to a report issued today.
Moreover, the risk for cancer increases even with modest weight gain, said Walter C. Willett, M.D., Ph.D., of the Harvard School of Public Health. He said excess body fat increased the risk for cancers of the colon, kidney, and pancreas, adenocarcinoma of the esophagus and endometrium, and breast cancer in postmenopausal women.
That was the major finding from a mega-analysis of more than 7,000 published studies conducted by a 21-member board assembled by the American Institute for Cancer Research and the World Cancer Research Fund International.
The results of the analysis, Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, were released at a press conference here.
Dr. Willett pointed out that obesity is now the second leading cause of cancer, just behind tobacco, because "obesity increases the risk of so many cancers and because two-thirds of Americans are overweight."
He and his colleagues predicted that over the next decade "obesity will become the number one risk factor for cancer" as obesity increases and the number of smokers decreases.
Dr. Willett said the finding was a call to action for clinicians, who he said should begin counseling patients about the danger of excess weight with "the first few pounds gained or first few extra inches of abdominal girth."
He faulted clinicians for failing to mention weight until patients need to lose 30 pounds or more, which he said was the wrong approach.
In addition to excess weight, Dr. Willett and colleagues said that 18 ounces of red meat per week was a safe amount but for every 1.7 additional ounces consumed per week the risk of cancer increased by 15%.
For processed meats, the panelists said it was not able to identify a safe level. "Every 1.7 ounces of processed meats consumed per day increased the risk of colorectal cancer by 21%," they said.
Dr. Willett said that alcohol was also linked to a variety of cancers and in some cases -- older women for example -- the risk of breast cancer begins to increase at levels as low as a single glass of wine per day.
How clinicians should balance the risk of breast cancer against the reported cardiovascular benefit of a daily glass of red wine is problematic, Dr. Willett admitted. But he said that folic acid consumption appeared to counterbalance the increased risk associated with alcohol.
His advice to patients who want the heart protective benefit of red wine is to take a multivitamin daily. "I believe that will offset the increased risk."
On the basis of the analysis, the panelists issued these 10 recommendations for cancer prevention:
Be lean as possible within the normal range of body weight.
Be physically active as part of everyday life.
Limit consumption of energy-dense foods. Avoid sugary drinks.
Eat mostly foods of plant origin.
Limit alcoholic drinks.
Limit consumption of salt. Avoid moldy cereals (grains) or pulses (legumes).
Aim to meet nutritional needs through diet alone.
Women of childbearing age should plan to breastfeed and children should be breastfed.
Cancer survivors should follow the recommendations for cancer prevention.
AICR supports research and educational programs focused on diet and cancer. It is a member of the World Cancer Research Fund International, which along with AICR funded the analysis. Additional source: American Institute for Cancer Research and World Cancer Research Fund InternationalSource reference: World Cancer Research Fund, American Institute for Cancer Research, "Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective" 2007.