From OncoLog, Feburary/March 2005, Vol. 50, No. 2/3

OBESITY
A Weighty Contributor to Cancer

In the 1990s, the World Health Organization began sounding the alarm about a worldwide epidemic of obesity. At the time, it might have sounded like Chicken Little warning that the sky was falling, but the statistics reveal the truth: In 1995, there were an estimated 200 million obese adults worldwide; by 2000, the total had risen to 300 million.

It is widely known that obesity contributes to serious health problems, especially cardiovascular disease and diabetes mellitus. Another side effect of obesity that has drawn less attention is its link to cancer. Research from the American Cancer Society (ACS) suggests that, at least in the United States, obesity is responsible for 20% of all cancer deaths in women and 14% in men. The ACS further estimates that 90,000 people each year are dying from obesity-related cancers.

In the United States, research in 2000 showed that 65% of all adults were overweight. Of those, 31% were obese. The categories were based on body mass index (BMI), a measure of weight adjusted for height. People with a BMI of 18.5 to 24.9 are considered normal weight, those with a BMI of 25.0 to 29.9 are considered overweight, and those with a BMI over 30.0 are considered obese. Thus, a man 5 feet 11 inches tall and tipping the scales at 215 pounds is obese, as is a woman 5 feet 3 inches tall and 169 pounds. The upper limit of normal weight is 178 pounds for a man who is 5 feet 11 inches tall and 140 pounds for a woman 5 feet 3 inches tall.

Higher death rates

A study published in 2003 in the New England Journal of Medicine showed that obese men had cancer death rates that were 52% higher than those of normal-weight men. For women, the news was even worse, with obese women dying of cancer at a rate 62% higher than that for normal-weight women.

The findings of that study also reinforced earlier reports indicating a link between obesity and cancers of the breast, colon, esophagus, gallbladder, kidney, rectum, and uterus. The study connected obesity with several types of cancer that had not been previously linked to excess body weight: cancers of the cervix, liver, ovaries, pancreas, prostate, and stomach, plus non-Hodgkin’s lymphoma and multiple myeloma. Women’s risk of breast cancer is doubly affected because obesity not only increases the risk of developing breast cancer but also of dying from it.

Another ACS study showed that Americans seem unaware of the link between obesity and cancer. A survey conducted in 2002 showed that only 1% of the respondents knew that maintaining a healthy weight was an effective way to reduce their risk of cancer.

Possible links

The mechanism of the link between body weight and cancer is not clear, but some researchers suspect a hormonal connection. Obesity may trigger the beginnings of cancer by increasing the levels of hormones such as estrogen or insulin. A disruption of insulin metabolism, for example, can increase the risk for colon cancer. Other components of a person’s diet can affect inflammatory response, the metabolism of carcinogens, cell death, and DNA repair, all of which can be involved in the development or progression of several types of cancer.

For more information on this topic or for questions about M. D. Anderson’s treatments, programs, or services, call askMDAnderson at (877) MDA-6789.

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