Introduction
Excess body weight (body mass index [BMI] ≥ 25.00 kg/m2) is an established
risk factor for diabetes, hypertension and cardiovascular disease, but its relationship
to cancer is lesser-known. This study used population attributable fractions (PAFs)
to estimate the cancer burden attributable to excess body weight in Canadian adults
(aged 25+ years) in 2010.
Methods
We estimated PAFs using relative risk (RR) estimates from the World Cancer
Research Fund International Continuous Update Project, BMI-based estimates of overweight
(25.00 kg/m2–29.99 kg/m2) and obesity (30.00+ kg/m2) from the 2000–2001 Canadian
Community Health Survey, and cancer case counts from the Canadian Cancer Registry.
PAFs were based on BMI corrected for the bias in self-reported height and weight.
Results
In Canada in 2010, an estimated 9645 cancer cases were attributable to excess
body weight, representing 5.7% of all cancer cases (males 4.9%, females 6.5%). When
limiting the analysis to types of cancer associated with high BMI, the PAF increased to
14.9% (males 17.5%, females 13.3%). Types of cancer with the highest PAFs were
esophageal adenocarcinoma (42.2%), kidney (25.4%), gastric cardia (20.7%), liver
(20.5%), colon (20.5%) and gallbladder (20.2%) for males, and esophageal adenocarcinoma
(36.1%), uterus (35.2%), gallbladder (23.7%) and kidney (23.0%) for females.
Types of cancer with the greatest number of attributable cases were colon (1445), kidney
(780) and advanced prostate (515) for males, and uterus (1825), postmenopausal
breast (1765) and colon (675) for females. Irrespective of sex or type of cancer, PAFs
were highest in the Prairies (except Alberta) and the Atlantic region and lowest in
British Columbia and Quebec.
Conclusion
The cancer burden attributable to excess body weight is substantial and
will continue to rise in the near future because of the rising prevalence of overweight
and obesity in Canada.