Obesity, Physical Inactivity Drive up Cancer Numbers: study

CALGARY — Every year in Canada, more than 12,000 people develop cancer because of excess body weight and physical inactivity, according to new research by Alberta Health Services (AHS).

Of that number – equivalent to the population of Canmore – more women than men are affected.

“Obesity and physical inactivity are well-known risk factors for diabetes and cardiovascular disease, but people may tend to overlook the role they play in the development of cancer,” says Dr. Darren Brenner, an AHS epidemiologist and the author of the study.

“The evidence is clear that thousands of cancers could be prevented each year if people paid more attention to diet and exercise.”

The research is believed to be the most comprehensive, quantitative estimate of disease burden in Canada due to these two related factors. It found that in 2007, the period studied, 5,771 cancer cases were attributed to excess body weight and 12,885 to physical inactivity.

Dr. Brenner says there is likely a great deal of overlap between the two groups, but it’s difficult to estimate how much. The research also shows a strong relationship between weight and risk of developing cancer – the greater the excess weight, the greater the risk.

Previous research has suggested that energy imbalance – taking in more calories through food than are burned through physical activity – can cause several different types of cancer.

Dr. Brenner says one of the most alarming figures is that only about 15 to 20 per cent of people meet the minimum amount of physical activity recommended for cancer prevention.

“It’s shocking how few people are getting enough exercise,” he says.

Health Canada and the American Cancer Society both recommend a minimum of 150 minutes of moderate to vigorous physical activity a week. High-intensity walking, for example, would count as moderate physical activity.

“For many years now, researchers in this area have been highlighting the associations between physical inactivity and cancer,” says Dr. Christine Friedenreich, Scientific Leader for the Department of Cancer Epidemiology and Prevention Research with AHS, whose international research program has been examining this topic since 1995.

“This study provides a sobering perspective on the magnitude of the problem of physical inactivity and obesity on cancer incidence in Canada. The findings should serve as additional incentive to help everyone incorporate physical activity into their daily routines.”

Another important finding is that the burden of disease due to the two risk factors is greater among women than men. Gender-specific cancers, such as cancer of the breast or endometrium, have strong associations with excess weight and physical inactivity, contributing to these differences in burden, Dr. Brenner says.

In Alberta, about 16,000 cancer cases are diagnosed every year.

In the next phases, researchers plan to break the numbers down by province and, in Alberta, by AHS zone to show how many cancer cases are a result of obesity and physical inactivity.

Earlier this year, AHS launched a website, albertapreventscancer.ca, to give Albertans the facts about accessible and achievable choices they can make every day to reduce their cancer risk.

The research study was published in the September issue of the journal Preventive Medicine and appeared online in advance of its publication.

Alberta Health Services is the provincial health authority responsible for planning and delivering health supports and services for more than four million adults and children living in Alberta. Its mission is to provide a patient-focused, quality health system that is accessible and sustainable for all Albertans.

(Alberta Health Services)