A recent seminar about the role of obesity on breast cancer got me thinking about how weight affects all types of cancer. In the United States, where a third of people are obese, many patients experience weight-related complications in cancer diagnosis and treatment. Obesity increases the risk and mortality rates for colon, breast, endometrial, kidney, esophageal, and other cancers. As unhealthy weights are increasing throughout most of the world, it is important to understand the relationship weight plays on cancer occurrence, treatment, and oncofertility.
In some cases, the link between cancer and obesity is well understood. Adipose tissue, or fat, produces the hormone estrogen that can increase the proliferation of some cancer cells. Hormone-responsive breast tumors are especially sensitive to estrogen, causing obese women to have a 50% increased risk for breast cancer than healthy weight women. Weight loss is negatively correlated with breast cancers, which gives women an opportunity to immediately reduce their cancer risk. Persistently high insulin levels caused by weight gain may also increase the risk for some cancers, including colorectal cancer.
Other cancers are correlated with increased cancer risk but have unknown etiology. For example, a type of esophageal cancer, called adenocarcinoma, and some stomach cancers are linked to obesity, possibly through gastric reflux disease, but no biological mechanism has further explained this link.
In addition to increasing the prospect of developing cancer, obesity can reduce the ability to diagnose abnormally dividing cells. This is because a variety of cancers, including those of the prostate and breast, are less likely to be detected in obese men and women. Obesity is correlated with reduced survivorship in these types of cancers.
Once diagnosed, obesity may continue to impact treatment success. Many chemotherapy does are calculated by body surface area rather than weight, which may lead obese people to receive ineffective doses of chemotherapy. One study also suggests that cancerous cells might not receive full doses of radiation in obese people.
Survivors can benefit from weight loss even after beating cancer. Multiple studies describe an improved quality-of-life in cancer survivors of healthy rather than obese weights. As we all know, fertility is one of the most important issues to young cancer survivors, who already have reduced chances for achieving a spontaneous pregnancy. By itself, obesity can reduce testosterone levels in men and cause ovulation and other conception problems for women, thus inhibiting fertility. Fortunately, survivors can be proactive in this oncofertility issue by developing healthy eating and exercise habits to pass on to the next generation.