caloric restriction substantially affects lifespan in many animals, including the ability to delay or prevent many age-related diseases. typically, this involves caloric intake of 60–70% of what an "ad libitum" animal would consume, while still maintaining proper nutrient intake. in rodents, this has been shown to increase lifespan by up to 50%; similar effects occur for yeast and "drosophila". no lifespan data exist for humans on a calorie-restricted diet, but several reports support protection from age-related diseases. two major ongoing studies on rhesus monkeys initially revealed disparate results; while one study, by the university of wisconsin, showed that caloric restriction does extend lifespan, the second study, by the national institute on aging (nia), found no effects of caloric restriction on longevity. both studies nevertheless showed improvement in a number of health parameters. notwithstanding the similarly low calorie intake, the diet composition differed between the two studies (notably a high sucrose content in the wisconsin study), and the monkeys have different origins (india, china), initially suggesting that genetics and dietary composition, not merely a decrease in calories, are factors in longevity. however, in a comparative analysis in 2014, the wisconsin researchers found that the allegedly non-starved nia control monkeys in fact are moderately underweight when compared with other monkey populations, and argued this was due to the nia's apportioned feeding protocol in contrast to wisconsin's truly unrestricted "ad libitum" feeding protocol. they conclude that moderate calorie restriction rather than extreme calorie restriction is sufficient to produce the observed health and longevity benefits in the studied rhesus monkeys.