The percentage of overweight and obese adults and children has been steadily increasing over the past few decades. According to the National Cancer Institute, nearly one-third of all adults are now classified as obese.
This reflects an increase of 7.6 percentage points since 1994. Experts have concluded the chief causes of obesity are a sedentary lifestyle combined with an over consumption of foods high in fat and calories.
Obese people have an abnormally high and unhealthy proportion of body fat. To measure obesity, researchers commonly use a formula combining weight and height known as the body mass index (BMI). BMI provides a more accurate measure of obesity (30 points or more) or being overweight (25 to 29.9 points) than does weight alone.
Obesity increases the risk of breast cancer in post-menopausal women, shortens the time between return of the disease and lowers overall survival rates. Obesity and physical inactivity may account for 25 to 30 percent of several major cancers.
In 2001, experts concluded that cancers of the colon, breast (postmenopausal), endometrium (the lining of the uterus), kidney, and esophagus are associated with obesity. Some studies have also reported links between obesity and cancers of the gallbladder, ovaries, and pancreas.
The effect of obesity on breast cancer risk depends on a woman’s menopausal status. Before menopause, obese women actually have a lower risk of developing breast cancer than do lean women. However, after menopause, obese women’s risk of developing the disease balloons to 1.5 times the risk of healthy weight women.
That’s because experts have found Leptin, a hormone best known for its efforts to send messages to the brain to turn off hunger, plays a significant role in promoting breast cancer in obese women. In many people with obesity, the Leptin process may go awry. Rather than signaling no more food is needed, it instead stimulates the production of estrogen in breast tissue.
Obesity not only increases breast cancer risk but also morbidity rates from the disease as compared to the risk of lean women. Scientists estimate that about 11,000 to 18,000 deaths per year from breast cancer in U.S. women over age 50 might be avoided if women could maintain a BMI under 25 throughout their adult lives.
There is one caveat. Obesity seems to increase the risk of breast cancer only among postmenopausal women who do not use menopausal hormones. Among women who use menopausal hormones, there is no significant difference in breast cancer risk between obese women and women of a healthy weight.
Preventing excess weight gain can reduce the risk of many cancers. Experts recommend people establish habits of healthy eating and physical activity early in life to prevent obesity. Those who are already overweight or obese are advised to avoid additional weight gain, and to lose weight through a low-calorie diet and exercise. Even a weight loss of only 5 to 10 percent of total weight can provide substantial health benefits.
Azsunshinegirl, aka Lynette Summerill, is an award-winning journalist who lives in Scottsdale. In addition to writing about cancer-related issues, she writes a blog, Nonsmoking Nation, which follows global tobacco news and events.