Part of the rise of obesity in America can be linked to the availability of cheap food sold in bulk from warehouse stores like 
Walmart, says a 
study released this week by researchers from 
Georgia State University, the 
University of Iowa, the 
University of Virginia and the 
University of Louisville, . Wal-Mart is the biggest retailer in the U.S. and a staple of many rural areas. 
"We live in an environment with increasingly cheap and readily available junk food. We buy in bulk. We tend to have more food around. It takes more and more discipline and self-control to not let that influence your weight," Charles  Courtemanche, assistant professor of economics at Georgia State, told Danielle Paquette of 
The Washington Post.
Obesity  in America has surged from 1960, when 13 percent of adults were obese,  to 2012, when 35 percent of adults were, Paquette writes. The  first Walmart store opened in 1962, the first Sam's Club in 1983 and  the first Walmart supercenter in 1988. In addition to Walmart,  numerous other warehouse-style stores, like 
Target and 
Costco, have followed Walmart's lead by selling in bulk.
The study found that opening an additional Walmart store "per 100,000 residents increased an area’s  average body mass index by 0.24 units, or 10.8 percent of the sample  obesity rate," Paquette writes. Researchers wrote, “These estimates  imply that the proliferation of Walmart supercenters explains 10.5  percent of the rise in obesity since the late 1980s.” (
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(Growth of Wal-Mart since 1962)(Growth of Walmart since 1962)