LONDON, Ontario, April 18 (UPI) -- Canadian researchers warn some urban areas lack supermarkets and are at risk of becoming "food deserts."

The researchers say people living in areas lacking supermarkets pay almost double the price as their supermarket shopping counterparts for supplies from small local convenience stores.

Using geographic mapping techniques, study authors Jason Gilliland and Kristian Larsen, both of The University of Western Ontario in London, Ontario, found several areas of London with limited access by foot or public transit to one of the city's 28 supermarkets.

The study, published in the International Journal of Health Geographics, also found fewer than 20 percent of urban core residents have supermarket access in London today, compared to more than 75 percent who had easy access to supermarkets back in l961.

"More and more supermarkets are building in newer suburbs and smaller food shops are disappearing from older neighborhoods leaving food deserts in their wake," Gilliland said in a statement.

"Poor people with no car can be severely adversely affected by living in food deserts and are more likely to suffer from bad health and low quality of life with diseases such as heart disease, diabetes and cancer."