Excess weight expected to become 2nd leading preventable cause of cancer, after tobacco

A nationwide study led by researchers at the University of Calgary and Alberta Health Services in partnership with the Canadian Cancer Society (CCS) finds that unless government policy-makers and individuals make changes, excess weight will become the second-leading preventable cause of cancer, following tobacco.

The Canadian Population Attributable Risk of Cancer (ComPARe) study is the most comprehensive, up-to-date study on the preventable burden of cancer in Canada. It’s estimated that by 2042, the number of cancer cases due to excess weight will nearly triple, from 7,200 to 21,200. Currently, more than one in two Canadian adults are not at a healthy body weight, putting them at increased risk for at least 13 different types of cancer, including breast, colorectal, endometrial, and esophageal.

“This study has clearly demonstrated that nearly 40 per cent of cancers can be prevented, which gives us much hope for the future of cancer control,” says Dr. Christine Friedenreich, PhD, adjunct professor in the departments of Oncology and Community Health Sciences at the Cumming School of Medicine (CSM) and scientific director in the Department of Cancer Epidemiology and Prevention Research at Alberta Health Services. “We expect results from this study will guide further research, inform program development, and assist in advocating for new policies and programs aimed at decreasing the preventable burden of cancer in Canada.” 

The ComPARe study is the first study of its kind in Canada. The collaboration involved experts in epidemiology, biostatistics, cancer risk factors, cancer prevention and knowledge translation. Researchers focused on the current and future burden of more than 30 different cancer types due to more than 20 different modifiable cancer risk factors.

“Not all cancers are preventable, but some are. We hope that these results will encourage Canadians to  reduce their cancer risk through healthier choices, including being more physically active and practising sun safety,” says Dr. Darren Brenner, PhD, assistant professor in the departments of oncology and community health sciences at the CSM. “The findings show if we don’t act now, by 2042 about 60 per cent more cancer cases will be due to preventable causes.”

For example, if more Canadians had a healthy body weight, about 110,600 cases of cancer could be prevented by 2042. The causes of excess weight are complex and encompass social, economic, physiological, environmental and political factors. The CCS suggests no one policy option is going to solve the increasing incidence of overweight and obesity in Canada. The CCS funded the study and recommends that a comprehensive, societal approach be used and that Canadians should check with their doctors about what a healthy weight might be for them. 

“We are committed to improving and saving lives, and preventing cancer is an important part of this commitment,” says Dr. Leah Smith, PhD, senior manager, surveillance at CCS. “This new study gives us insight into where we can make the biggest difference in cancer prevention for Canadians so they can live their lives to the fullest.”

The ComPARe study showed that currently the top five leading preventable causes of cancer are smoking tobacco, followed by physical inactivity, excess weight, low fruit consumption, and sun exposure.

The CCS has developed a website with more information on the results of the ComPARe study. Findings from the study are also published in a special issue of Preventive Medicine.

Drs. Friedenreich and Brenner were co-principal investigators on the ComPARe study. They are also both members of the Arnie Charbonneau Cancer Institute and the O’Brien Institute for Public Health at the CSM.