As the New Year approaches, many will make—and break—their New Year’s resolutions. A new study should provide motivation for a resolution regarding shedding those excess pounds. It reported that being overweight increases the risk of cancer; it also pinpointed which types of fat were most likely to cause cancer and which individuals were at the most risk. The study was published on December 4 in the journal Applied Physiology, Nutrition, and Metabolism by researchers at the National Institute on Aging (Bethesda, Maryland).
The researchers note that excess poundage is a significant risk factor for developing cancer. They cited a large meta-analysis of more than 280,000 cancer cases, which reported that a greater body mass index (BMI) was associated with increased risk of many types of cancer (A meta-analysis is a review of several studies on a topic to clarify the data.) The meta-analysis and several other studies have reported that particularly strong evidence of increased risk exists for cancers of the breast, endometrium (uterine lining), esophagus, pancreas, colon and rectum, kidney, thyroid, and gallbladder. The investigators noted that the use of BMI for determining overweight status has limitations because it does not provide information regarding where the excess adipose tissue is located. In addition, variations in height and build can skew the results. For example, an individual who is shorter and very muscular may weigh enough that their BMI would categorize them as overweight or obese; however, this person might actually have very little body fat.
The investigators conducted a study that measured BMI as well as the following: total adipose tissue from dual-energy X-ray absorptiometry, computed tomography measures of visceral adipose tissue (VAT; the fat that surrounds vital organs in the abdominal cavity); abdominal subcutaneous adipose tissue; thigh intermuscular adipose tissue; and thigh muscle attenuation (Hounsfield unit; HU), where low HU indicates infiltration of fat into the muscle. The study group comprised 2,519 individuals (1,179 men; 1,340 women), initially aged 70 to 79 years and without cancer who were enrolled in the Health, Aging, and Body Composition Study, which was a prospective (forward-looking) study supported by the National Institute on Aging. The subjects were followed for 13 years.
In general, the investigators found that both men and women with greater body fat had an increased risk of developing cancer, regardless of their BMI. In fact, they found that increased body fat increased the risk for many types of cancers, even beyond those categorized as obesity-related by the National Cancer Institute. Specifically, they found that men with elevated levels of visceral fat had a particularly high risk of cancer, compared to men with low levels of visceral fat. According to the study, men with this type of fat had a three times greater risk of developing certain types of cancers, including those of the esophagus, pancreas, colon and rectum, kidney, thyroid, and gallbladder.
The study authors concluded that, although the underlying reasons are unclear, the results of the study suggest that excess body fat may increase the risk for cancer in older men and women; however, VAT was strongly associated with cancer in men beyond that attributed to BMI. They noted that, in addition, the study suggests differential associations between adiposity and risk among men and women.