The growing worldwide obesity epidemic has been blamed on a number of factors, but a study argues that it may be inexorably linked with wealthy nations and their fast-food restaurants.

Researchers compared the number of fast-food restaurants per capita in 26 countries listed as advanced economies by the International Monetary Fund. They used one chain (Subway) as a proxy measure; at the end of 2010 the chain reportedly had the most restaurants worldwide.

Countries with the highest density of restaurants per capita were the U.S. and Canada: 7.52 and 7.43 per 100,000 people, respectively. In the U.S. the prevalence of obesity for men and women is about 32%, while in Canada it’s about 23%.

Japan, however, has far fewer of the fast-food restaurants, 0.13 per 100,000 people, and a far lower obesity rate: 2.9% for men and 3.3% for women. Similarly, Norway has 0.19 restaurants per 100,000 people and an obesity rate of 6.4% for men and 5.9% for women.


The researchers, who emphasize that the findings show correlation and not causality, controlled for various factors such as the number of people living in urban areas, income, Internet use and the number of motor vehicles per capita.

Obesity is often linked with environmental factors as well as genetic ones. The popularity of sugary drinks, the loss of physical education in school, more sedentary jobs and extra time spent in front of computers and television have been blamed, as well as certain genes that may affect how our bodies process food.

“In my opinion the public debate is too much focused on individual genetics and other individual factors, and overlooks the global forces in society that are shaping behaviors worldwide,” said lead author Roberto De Vogli of the University of Michigan School of Public Health in a news release. “If you look at trends over time for obesity, it’s shocking.”

The study was published in the December issue of the journal Critical Public Health.