CANCER
August 26, 2014

A Cancer-Obesity Connection

It's not just about your heart. Many types of cancer are far more likely to occur as your body mass index (BMI) rises.

It is a well known fact that being overweight or obese increases a person’s chances of developing diseases like hypertension, heart disease, stroke, and type 2 diabetes, but there is also a very strong link between being overweight and the likelihood of developing certain cancers.

The obesity epidemic is causing over 12,000 cases of cancer annually because a high body mass index (BMI) significantly raises the risk of developing 10 of the most common cancers, according to new research.

Researchers used data from the records of general practitioners to identify over five million people 16 years and older who did not have cancer and who had been monitored for an average of 7.5 years. They calculated the risk of developing 22 of the most common cancers according to BMI, taking into consideration such factors as age, gender, whether a person smokes or not, and socioeconomic status.

Higher BMI was associated with an increased risk of cancers of the uterus, gallbladder, kidney, cervix, thyroid, as well as leukemia. The risks for developing liver cancer, colon cancer, and ovarian cancer were also associated with a higher BMI.

Nearly 167,000 people developed one of the 22 cancers examined during the follow-up period. BMI was positively linked with 17 of those cancers. In other words, the likelihood of developing them went up as BMI increased.

Higher BMI was associated with an increased risk of cancers of the uterus, gallbladder, kidney, cervix, thyroid, as well as leukemia. The risk of developing liver cancer, colon cancer, and ovarian cancer was also associated with a higher BMI.

Even within normal BMI ranges, a higher BMI was associated with an increased risk of some forms of cancer. The study found some evidence that people with a high BMI had a slightly lowered risk of prostate cancer and premenopausal breast cancer.

Not all cancer risk increases with BMI. According to lead author Krishnan Bhaskaran, “There was a lot of variation in the effects of BMI on different cancers. For example, risk of cancer of the uterus increased substantially at higher body mass index; for other cancers, we saw more modest increases in risk, or no effect at all.

“For some cancers like breast cancer occurring in younger women before the menopause, there even seemed to be a lower risk at higher BMI. This variation tells us that BMI must affect cancer risk through a number of different processes, depending on the cancer type.”

The researchers, from the London School of Hygiene & Tropical Medicine and the Farr Institute of Health Informatics, estimate that an extra 8- to 10-pound weight gain in adults, which happens roughly every 12 years based on recent trends, would lead to nearly 4,000 more cases of cancer per year by 2026.

More than a third of US adults are obese, and the United States is the fattest nation in the world. Though this study was carried out in the United Kingdom, there is no reason to think that the results would not apply to Americans as well.

In his comments on the study, Dr. Peter Campbell of the American Cancer Society noted that there was plenty of “evidence that obesity is an important cause of unnecessary suffering and death from many forms of cancer. More research is not needed to justify, or even demand, policy changes aimed at curbing overweight and obesity,” such as those simply encouraging physical activity or the restriction of nutritionally sparse foods (such as sugar-sweetened beverages).

What is needed, he wrote, are interventions and policies that reduce overweight and obesity, and politicians with sufficient courage, to implement such policies effectively.

The study is published in The Lancet.

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