A key difference between the two monkey trials was that in the 2009 study, conducted at the University of Wisconsin, the calorie-restricted animals only received one meal a day and the researchers took away any leftover food in the late afternoon, so the animals were forced to fast for about 16 hours. In the 2012 study, run by the National Institute on Aging, the animals were fed twice a day and the food was left out overnight. The Wisconsin monkeys were the ones that lived longer.
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