Most common site-specific cancers linked to weight
Dr .Krishnan Bhaskaran, MSc, PhD, National Institute for Health Research Postdoctoral Fellow, from the London School of Hygiene & Tropical Medicine, London, UK and lead author of study along with colleagues examined the links between BMI and the most common site-specific cancers.
Researchers collected data from the UK Clinical Practice Research Datalink (CPRD) and identified 5·24 million individuals aged 16 and older who were cancer-free and had been followed for an average of 7·5 years. BMI was calculated directly from weight and height records. The team had examined the associations between BMI and 22 of the most common cancers, and adjusted for confounders.
A total of 166, 955 participants had developed cancer. BMI was associated with 17 of 22 cancers, but effects varied substantially by site.
Each 5 kg/m2 increase in BMI was clearly linked with higher risk of cancers of the uterus (62% increase), gallbladder (31%), kidney (25%), cervix (10%), thyroid (9%), and leukemia (9%). A higher BMI also increased the overall risk of liver (19% increase), colon (10%), ovarian (9%), and breast cancers (5%), but the effects on these cancers varied by underlying BMI and by individual-level factors such as sex and menopausal status. Even within normal BMI ranges, higher BMI was associated with increased risk of some cancers.
There was some evidence that those with high BMI were at a slightly reduced risk of prostate cancer and premenopausal breast cancer.
Dr. Bhaskaran commented “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 also estimated that 41% of uterine and 10% or more of gallbladder, kidney, liver, and colon cancers could be attributable to excess weight.
The researchers estimated that a 1 kg/m2 (about 8 or 10 pounds per adult) population-wide increase in BMI would result in 3,790 additional annual UK patients developing one of the ten cancers positively associated with BMI.
Dr. Peter Campbell, PhD, Director of the Tumor Repository from the American Cancer Society, Atlanta, USA, in a linked comment had wrote "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.”
This study is published in The Lancet.