The obesity crisis is worse in the United States than in Canada, a new study of rates in both countries shows.

Obesity is increasing in both Canada and the U.S., the researchers found. But less than a quarter of Canadian adults (24.1 per cent) are obese, compared to more than a third (34.4 per cent) of U.S. adults.

The comparison was a joint effort from Statistics Canada and the U.S. Centers for Disease Control and Preventions National Center for Health Statistics and appears in the NCHS's March Data Brief.

Obesity was defined as a body mass index (BMI) of 30.0 or higher.

The researchers found that among Canadian men, 24.3 per cent are considered obese, compared with 32.6 per cent of their American counterparts.

The gap was even wider among women: 23.9 per cent of Canadian women were obese between 2007 and 2009, compared with 36.2 per cent of women in the United States.

The prevalence of obesity among men has increased over the past two decades by about 10 percentage points in Canada and 12 percentage points in the U.S. The percentage changes among women were eight and 10, respectively.

Among men, the increase in both countries has been highest among seniors, aged 60 to 74. But among women, the increase has been highest among those much younger: those in the 20 to 39 category.

The study authors point out that the ethnic mix in each country is different. The American non-white population is comprised mainly of Hispanics and blacks, they noted, who are more likely to become obese than white Americans.

In contrast, Canadian non-whites are composed primarily of East/Southeast Asians, who are less likely to become obese than white Canadians.

The researchers used data collected by the U.S. National Health and Nutrition Examination Survey as well as the Canadian Health Measures Survey.

In the United States, the surveys were conducted between 1988 and 1994 and then again between 2007 and 2008. In Canada, numbers were gathered between 1986 and 1992, as well as between 2007 and 2009.