In a new survey, 90 percent of Americans say most other Americans are overweight. But only 39 percent see themselves as so, leaving at least an 11 percent discrepancy in perceptions.

Also interesting: Only 70 percent said the people they know are overweight.

The telephone survey of 2,250 adults, released today, was conducted by the Pew Research Center.

Most respondents believe that gains in girth owe largely to personal behavior — lack of exercise topped the list, followed by a lack of willpower to control diet — rather than genetics or marketing by food companies.

Only a third said they thought genetics and heredity were responsible.

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