Higher BMI associated with 10 common cancers

by Thomas R. Collins – After evaluating data on 5 million adults in the UK, researchers concluded that an increasing body mass index (BMI) raises the odds of developing 10 of the most common cancers. The findings were published on Aug.13, 2014 in The Lancet.

“The number of people who are overweight or obese is rapidly increasing both in the UK and worldwide. It is well recognised that this is likely to cause more diabetes and cardiovascular disease. Our results show that if these trends continue, we can also expect to see substantially more cancers as a result”, said study leader Dr. Krishnan Bhaskaran, National Institute for Health Research Postdoctoral Fellow, London School of Hygiene & Tropical Medicine, London, UK.

The investigators evaluated data in the UK’s Clinical Practice Research Datalink (CPRD). They studied 5.24 million individuals aged 16 and older who were cancer-free at baseline and had been followed for an average of 7.5 years.

They reported that 166, 955 people developed one of the 22 cancers studied over the follow-up period.

BMI was associated with 17 out of the 22 cancers. Each 5 kg/m² increase in BMI was linked with higher risk of cancers of the uterus (62% increase), gallbladder (31%), kidney (25%), cervix (10%), thyroid (9%), and leukemia (9%).

Higher BMI also increased the overall risk of liver (19% increase), colon (10%), ovarian (9%), and breast cancers (5%). The risk of these cancers varied by underlying BMI and by sex and menopausal status. Some evidence suggested that high BMI slightly reduced risk of prostate cancer and premenopausal breast cancer.

Bhaskaran added, “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 concluded that excess weight could account for 41% of uterine and 10% or more of gallbladder, kidney, liver, and colon cancers in the UK.

Writing in a linked Comment, Dr. Peter Campbell from the American Cancer Society said, “We have sufficient 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. Some of these policy strategies have been enumerated recently, all of which focus on reducing caloric intake or increasing physical activity, and include taxes on calorically dense, nutritionally sparse foods (eg, sugar-sweetened beverages); subsidies for healthier foods, especially in economically disadvantaged groups; agricultural policy changes; and urban planning aimed at encouraging walking and other modes of physical activity. Research strategies that identify population-wide or community-based interventions and policies that effectively reduce overweight and obesity should be particularly encouraged and supported. Moreover, we need a political environment, and politicians with sufficient courage, to implement such policies effectively.”