Published today in the Canadian Journal of Public Health, the study provides the first comprehensive look at adult obesity rates across Canada since 1998, complete with "obesity maps."

"Being obese or overweight significantly increases the risk of chronic illnesses, such as heart disease, diabetes, and some cancers," says study lead author, Prof. Carolyn Gotay in UBC's School of Population and Public Health. "Our analysis shows that more Canadians are obese than ever before -- on average, between one fourth and one third of Canadians are obese, depending on the region."

The Maritimes and the two Territories had the highest obesity rates from 2000 to 2011 -- more than 30 per cent of the population in these regions is estimated to be obese. British Columbia had the lowest overall rates, but obesity still increased from less than 20 per cent to almost 25 per cent. Meanwhile, rates in Quebec remained below 24 per cent.

The obesity maps that accompany the study serve as a tool to regional authorities to monitor and act on these trends, says Gotay, who is also the Canadian Cancer Society Chair in Cancer Primary Prevention in UBC's Faculty of Medicine.

"Maps that use colours and well-known geographical depictions are an efficient way to convey complex data that transcends language differences and personalizes the data for the viewer," says Gotay. "This information can provide an impetus for action for the public, health care providers, and decision makers."

Using data from the Canadian Community Health Survey, the researchers adjusted self-reported Body Mass Index (BMI) data to get more accurate obesity estimates. Over the 11-year study period, the researchers found the greatest increase occurring between 2000 and 2007.