Excessive weight and obesity in particular is one of the several major risk factors for breast cancer. Good news is that unlike such breast cancer risk factorsAnything that increases or decreases a person’s chance of developing a disease. as heredity, it’s a risk factorAnything that increases or decreases a person’s chance of developing a disease. that can be prevented.
What is Obesity?
The National Institute of Health measures obesity by a formula called the body mass index (BMI). BMI is the ratio of one’s weight in kilograms to one’s height in meters. Adults over the age of 20 can be classified into 4 groups:
- Less than 18.5 BMI – Underweight
- 18.5-25 BMI – Normal
- 25-30 BMI – Overweight
- 30+ BMI – Obese
This chart helps determine your BMI. Find your height on the left or right side and your weight on the top or bottom. The point where these lines intersect reveals the category you fall in. You can also use the calculator below to find your body mass index. Obese individuals have a BMI of over 30.
[Chart courtesy of Wikimedia Commons]
Who Is At Risk For Obesity?
Anyone is at risk for obesity. Obesity is, in fact, becoming more and more common in the U.S. According to the 2007–2008 National Health and Nutrition Examination Survey (NHANES), over one-third (33.8%) of the U.S. adult population aged 20-74 is obese. This rate shows an alarming upward trend from the 13.4% rate in the 1960-1962 survey and the 22.9% rate in the 1988-1994 survey. In 2007-2008, Mexican-American women (45.1%) and African-American women (49.6%) had a significantly higher rate of obesity. Common traits of those who are obese are a high-calorie diet and an inactive lifestyle.
How Obesity Increases Breast Cancer Risk: The Alarming Facts
A growing number of studies have shown a undeniable link between obesity and an increased risk of breast cancer. According to peer-reviewed medical studies compiled by the National Cancer Institute:
- Obesity and physical inactivity may account for 25 to 30 percent of postmenopausal breast cancer
- Preventing weight gain can reduce the risk of many cancers
- Even a weight loss of only 5 to 10 percent of total weight can provide health benefits
- 3.2 percent of all new cancers are linked to obesity
- In 2002, about 41,000 new cases of cancer in the United States were estimated to be due to obesity
- A recent report estimated that, in the United States, 14 percent of deaths from cancer in men and 20 percent of deaths in women were due to overweight and obesity
- After menopauseThe end of a woman’s menstrual cycles, defined as 12 consecutive months of no menstrual periods., obese women have 1.5 times the risk of breast cancer of women of a healthy weight
- 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
- Weight gain during adulthood has been found to be the most consistent and strongest predictor of breast cancer risk in studies in which it has been examined
- Women with a large amount of abdominal fat have a greater breast cancer risk than those whose fat is distributed over the hips, buttocks, and lower extremities
- Both the increased risk of developing breast cancer and dying from it after menopause are believed to be due to increased levels of estrogenA female sex hormone that is primarily produced by the ovaries. Its primary function is to regulate the menstrual cycle and assist in the production of secondary sex characteristics such as breasts. It may even play a role in the production of cancer cells in the breast tissue. in obese women; estrogen levels in postmenopausal women are 50 to 100 percent higher among heavy versus lean women
- Because breast tumorsA mass of cells that can be benign or malignant. are more difficult to detect in obese women, breast cancer is more likely to be detected at a later stage than lean women, leading to a higher breast cancer mortality rateThe measure of the number of deaths in a particular population. for obese women
- African-American women who have a high BMI are more likely to have an advanced stage of breast cancer at diagnosis
- Obese Hispanic white women were twice as likely to develop breast cancer as non-obese Hispanics
How Can I Reduce My Risk of Obesity & Breast Cancer?
If you are at a healthy weight already, maintain it. Periodically weigh yourself and be aware of lifestyle changes such as a new job, pregnancy, or a change in activity level that might effect your calorie expenditure or intake. Adjust your eating and exercise habits to allow for the changes.
If you are overweight or obese, it is never too late to lose weight. Ignore fad diets. Follow proven weight loss guidelines (eat less, exercise more) for long-lasting weight loss that will help reduce your risk of breast cancer. Consider eating more anti-cancer foods, many of which are low-calorie. Begin a workout schedule and eat less.
No matter what your weight, reduce your overall cancer risk by learning about the other risk factors for breast cancer, many of which are preventable.