Rising BMI May Increase Risk for Kidney Cancers

A new study shows yet another link between increasing body mass index (BMI) and the risk of several common cancers, including kidney cancer. Results showed that excess weight may account for 10% of kidney cancer cases diagnosed in the United Kingdom, where the study took place.

“The number of people who are overweight or obese is rapidly increasing both in the UK and worldwide. It is well recognized 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,” study leader Krishnan Bhaskaran, National Institute for Health Research Postdoctoral Fellow, from the London School of Hygiene & Tropical Medicine, London, UK, said in a press release.

Bhaskaran and colleagues used primary care data from more than 5 million individuals in the United Kingdom in the Clinical Practice Research Datalink to investigate associations between BMI and 22 cancer types.

Of the 5.24 million individuals included, 166,955 (3.2%) developed a cancer. The researchers found that BMI was linked with 17 of the 22 cancer types investigated. Specifically, each 5 kg/m² increase in BMI was associated with an increased risk for kidney cancer (hazard ratio [HR] = 1.25; 95% CI, 1.17-1.33; P < .001). Increasing BMI was also found to be associated with uterine, gallbladder, cervical, and thyroid cancers, as well as leukemia.

Assuming that the association between BMI and cancer risk were causal, the researchers estimated that 10% of gallbladder, kidney, liver and colon cancers in the population are attributable to overweight or obesity. The researchers estimated that “a 1 kg/m² population-wide increase in BMI would lead to 3,790 extra patients developing one of the ten cancers that had a net positive association with BMI.”

In an editorial that accompanied the article, Peter T. Campbell, PhD, of the American Cancer Society, wrote that confidence in the results of this study should be bolstered by the investigators’ sensitivity and model checking exercises, as well as the fact that many of the findings have been reported in previous studies. However, he also pointed out that selection bias may play a factor in this study as well since only about 50% of the initial cohort has sufficient BMI data and follow-up time.

“We have sufficient evidence that obesity is an important cause of unnecessary suffering and death from many forms of cancer, in addition to the well recognized increased risks of mortality and morbidity from many other causes,” Campbell wrote. “More research is not needed to justify, or even demand, policy changes aimed at curbing overweight and obesity.”

Instead, Campbell called for “research strategies that identify population-wide or community-based interventions and policies that effectively reduce overweight and obesity.”