A recent report in the Journal of Clinical Oncology presents some puzzling news — survivors of some types of cancer seem to be more prone to developing obesity than other people. It's well known that obesity itself can increase the risk of some types of cancer, such as breast and colorectal cancer, but the converse hasn't been widely recognized. Dr. Heather Greenlee from the Mailman School of Public Health at Columbia University and her colleagues analyzed data from the National Health Interview Survey (NHIS) from 1997 to 2014 to determine what happened to people who had survived various types of cancer.
The NHIS is an annual national survey in which a representative sample of Americans between the ages of 18 and 55 are telephoned and asked health-related questions. In this particular study, over 32,000 cancer survivors provided the data over the period between 1997 and 2014. The most common cancers were breast, prostate, and colorectal cancers.
Examining data by 2-yearly increments starting with 1997, the researchers found that at each point, cancer survivors — all cancers — were more likely to have BMIs greater than 30 (the cut point for obesity) than were those who hadn't had cancer. Although non-survivors also saw increases in BMIs over 30 at each time point, the increases were greater in cancer survivors. Over the entire 1997-2014 period, the obesity prevalence of those without a cancer history increased by 2.3 percent; for all cancers, the increase was 2.9 percent. But for colorectal cancer and breast cancer the increases were greater — 3.1 and 3.0 percent respectively. These increases were statistically greater than non-cancer respondents for all types of cancer. The biggest increase was seen in non-Hispanic black women.
Possible reasons for these differential increases included the effects of chemotherapy, hormonal therapy or steroid medications. Also, fatigue associated with treatments may mean that patients are less likely to be active. Whichever reason (or reasons) might explain the more rapid increase in weight for cancer survivors; the authors pointed out:
"Our findings suggest that the trajectory of the US obesity burden will continue to increase, which will result in an increased burden of obesity in the general population and thus increase the number of obesity-related cancers, and also result in an increased burden of obesity among cancer survivors, including those cancers in which obesity is associated with poorer cancer outcomes."
They also advise that effective weight management programs be planned and that physicians and others involved with cancer patients' care be aware and ready to cope with changes in body weight.