A Healthy Body Weight Reduces Cancer Risk

Huawei Zeng, Ph.D.

Everyone should know that obesity is both a national and global problem.  Two-thirds of Americans are overweight and one-third are obese.  A body mass index (BMI, which is the ratio of one's weight expressed in kilograms to the square of one's height expressed in meters, i.e., kg/m2) of 25 to 29.9 suggests overweight, while BMI values of 30 and above indicates obesity.  Worldwide, 2.3 billion people are estimated to be overweight or obese.

Everyone should also know that being obese increases risks for cardiovascular disease and type 2 diabetes.  But did you know that studies show being obese also increases the risk for cancer?  In fact, it is second only to smoking in that regard. As the prevalence of smoking declines, obesity is fast becoming the number one risk factor for cancer.

Cancer is thought to start with a change in the DNA in a single cell.  In fact, several such changes, called mutations, appear to be required over time in to initiate the cancer process, which ultimately involves the uncontrolled replication of the transformed cell. 

Body fat appears to promote carcinogenesis.  Adipose tissue, where body fat is stored, is metabolically active.  This tissue secretes a variety of hormones and other proteins that enter the blood stream to signal other cells and organs and promote inflammation and reduce responsiveness to insulin.  These effects, in turn, stimulate cells to grow and divide, which increases the frequency of DNA mutations and promotes the carcinogenic process. 

Research has shown that preventing the accumulation of excess body fat can reduce cancer risk. For most people, maintaining a healthy body weight can be achieved by moving more and eating well.

Consider physical activities such as brisk walking, biking, hiking, jogging or dancing for at least 30 minutes every day.  Find ways of incorporating physical activity in your daily schedule.  First, break it up to fit it in whenever you can. Three 10-minute walks are as beneficial as a single 30-minute walk. Second, seize every opportunity to add aerobic activities into your day such as parking in the farthest spot and taking the stairs instead of the elevator. Third, find a way to keep your physical activity fun. The more you enjoy it, the more likely you are to stick with it.

Eat smart by choosing a variety of foods especially vegetables, fruits, whole grains, beans and nuts.  Most plant foods are low in calories, which makes them particularly useful in managing body weight.  Plant foods also tend to contain significant amounts of vitamins, minerals, fiber and phytochemicals that strengthen the immune systems, reduce inflammation, and promote the elimination of potential carcinogens from the body. 

Evidence is mounting that the constituents of many plant foods interact to reduce cancer risk.  For example, the combined anticancer activity of cranberry and apple has been shown to be much greater than each when consumed individually. The American Institute for Cancer Research, or AICR, recommends limiting consumption of red and processed meats to 18 ounces (cooked weight) per week?that's no more than six 3-ounce servings weekly.  A 3-ounce serving is the size of a deck of cards.  This AICR-recommendation limits exposure to potential carcinogens in meats and also those produced when meats are cooked at high temperatures.

You can be assured of getting the optimal proportions of various foods by making your plate look like MyPlate.  Consult guidelines for healthy eating online at ChooseMyPlate.gov.  The AICR Guidelines for cancer prevention can be found at www.aicr.org.