In the other group, 80 percent of the monkeys given the same diet, but with 30 percent fewer calories, are still alive.

All of the animals in the study were enrolled as adults at ages ranging from seven to 14 years. Today, 33 animals remain in the study, said a UW-Madison release.

Of those, 13 are given free rein at the dinner table, and 20 are on a calorie-restricted diet. Rhesus macaques have an average life span of about 27 years in captivity. The oldest animal currently in the study is 29 years.

The new report was published in the Friday edition of Science.