Lead researcher Roberto De Vogli of the University of Michigan School of Public Health said the study of 26 wealthy nations found those with higher density of fast-food restaurants per capita had much higher obesity rates than those with a lower density of fast-food restaurants per capita.
"It's not by chance that countries with the highest obesity rates and fast-food restaurants are those in the forefront of market liberalization, such as the United States, the United Kingdom, Australia, New Zealand and Canada, versus countries like Japan and Norway, with more regulated and restrictive trade policies," De Vogli said in a statement.
The findings remain consistent even after factoring in income, income inequality, urban areas, motor vehicles and Internet use per capita, De Vogli said.
"Since the 1980s, and the advent of trade liberalization policies which indirectly promoted trans-national food companies ... we see (obesity) rates that have tripled or quadrupled. There is no biological, genetic, psychological or community level factor that can explain this. Only a global type of change can explain this," De Vogli said. "If you look at trends overtime for obesity, it's shocking."
The findings were published in the journal Critical Public Health.