Living Long on Less? Mouse and human cells respond to slim diets

Scientists have known since the 1930s that mice and other animals live 30 to 50 percent longer when placed on a diet that's low in calories yet nutritionally complete. The unanswered question has been whether calorie restriction has the same life-extending effect on people.

Direct proof of a payoff for human longevity would take decades. But scientists have now shown that people on a calorie-restricted diet experience many of the cellular changes reported in mouse studies.

"The experimental results [in mice] mirror the results we found," says Anthony E. Civitarese of the Pennington Biomedical Research Center in Baton Rouge, La. Whether those changes would extend a person's life remains uncertain, he notes.

As people get older, energy-converting organelles called mitochondria decrease in number and generate greater amounts of harmful by-products called free radicals. Many scientists hypothesize that DNA damage from these by-products can cause chronic diseases of ol