|Excess Weight Linked to 90,000 US Cancer Deaths Annually|
|Most Types of Cancers Affected By Weight|
|Article date: 2003/04/23|
Being overweight or obese substantially increases the risk of dying from cancer, according to researchers from the American Cancer Society.
In a new study published in Thursday�s New England Journal of Medicine (Vol. 348, No. 17: 1625-1638) researchers Eugenia Calle, PhD, and colleagues determined that overweight and obesity may account for 20% of all cancer deaths in US women and 14% in US men. That means 90,000 cancer deaths could be prevented each year if Americans could only maintain a normal, healthy body weight.
�As a society, we have not really acknowledged the contribution of obesity to chronic disease in general and cancer in particular,� said Calle, director of analytic epidemiology at the American Cancer Society. �We are not taking it seriously enough to turn it around. We are not acting on it.�
The researchers followed more than 900,000 men and women for 16 years to determine the role of weight in cancer deaths. They compared participants based on their body mass index, or BMI, a measure of weight adjusted for height. People with a BMI between 25 and 29.9 are considered overweight; those with a BMI of 30 or more are considered obese. People with a BMI between 18.5 and 24.9 are considered normal weight.
In the year 2000, about 65% of US adults were overweight or obese, according to the Centers for Disease Control and Prevention, and about 31% were obese.
Weight Plays A Greater Role Than Previously Known
Calle and her colleagues found that the heaviest men in the study had death rates from all cancers combined that were 52% higher than the rates among normal-weight men. The heaviest women had cancer death rates 62% higher than normal-weight women.
Their work also substantiated previous studies that linked overweight and obesity to cancers of the uterus, kidney, esophagus, gallbladder, colon and rectum, and breast (in postmenopausal women).
The effects on breast cancer are compounded, Calle said, because obesity increases a woman�s risk of developing the disease in the first place, and her risk of dying from it once she has it.
The researchers also found that many types of cancer that were not previously linked to obesity were, in fact, affected by excess body weight. Those included cancers of the liver, pancreas, prostate, cervix, ovary, and stomach (in men), as well as non-Hodgkin lymphoma and multiple myeloma.
�Overweight and obesity has a very broad impact on cancer across most cancer sites,� Calle said. �That�s not something that�s really in the consciousness of the American people.�
In fact, in an American Cancer Society survey conducted in 2002, just 1% of Americans identified maintaining a healthy weight as a way to reduce cancer risk.
Hormones A Factor
The researchers speculate that obesity acts on cancer by raising the body�s levels of hormones � sex hormones like estrogen, or protein hormones like insulin, and insulin-related growth factors. Too much fat around the waist, for instance, can disrupt insulin metabolism and increase the risk for colon cancer, among others, Calle said.
Losing weight has been shown to improve insulin sensitivity and to decrease the level of sex hormones in the blood, Calle said, so �it is reasonable to assume� that losing weight will also decrease cancer risk. However, she noted, too few people have been able to maintain a significant weight loss for that theory to be studied directly.
Losing weight might also help with a more obvious cancer-obesity link. Obesity can cause acid reflux, which can make a person more susceptible to esophageal cancer. Excess weight is also associated with gallstone formation, which increases the risk of gallbladder cancer.
Reducing The Obesity Risk
But Calle acknowledges that losing weight and keeping it off are increasingly difficult challenges.
�We have set up a society where people have to work very hard to eat right and get physical activity,� she said. People work long hours that leave little time for exercise or cooking healthy meals; Americans must rely heavily on cars to get around; sedentary activities like watching television or using the computer have become more common.
The American Cancer Society is doing its part to help people achieve a healthy weight by publishing guidelines for healthy eating and activity levels, she said. The Society recommends balancing calorie intake with physical activity by eating at least five servings of fruit and vegetables every day, choosing whole grains over processed grains, and limiting red meat. Adults should engage in at least 30 minutes of moderate physical activity five days a week or more.Additional Resources
Diet, Physical Activity and Cancer�What�s the Connection?