Many people intend to start eating right tomorrow, or the day after, or first thing next week. Adopting healthy habits can be a difficult process that often entails a number of missteps along the way. But new research provides incentive to keep trying. Findings published in the current issue of the journal Science indicate that starting a low-calorie diet at any point in adulthood lengthens life span--at least in fruit flies.

Previous research with organisms ranging from yeast to mammals has indicated that strict low-calorie diets helps to lengthen life span. Now Linda Partridge and her colleagues at University College London have shown that for fruit flies, the beneficial effects kick in as soon as the diet begins, regardless of what they were eating before. The researchers studied more than 7,000 flies and found that when the diet of regularly fed Drosophila was restricted, mortality dropped--within two days--to the same level as flies who had been on a limited diet their entire lives. Conversely, when flies that were calorically deprived since birth switched to a more robust diet, their rate of death rose to the level of generously fed flies. The results, according to the authors, show that the mortality of dieting flies "depends only upon their age and their current nutritional status, with past nutrition having no detectable effect."

Whether the same holds true for people remains unclear. The scientists caution that critical experiments in mammals, particularly rodents, have yet to be performed. But the findings do provide another impetus to reach for the veggies instead of the french fries. "Aging is so remarkably pliable that interventions do not have to be lifelong," observe James W. Vaupel of the Max Planck Institute for Demographic Research in Germany and colleagues in an accompanying commentary. "As illustrated by [this report] and other studies, interventions even late in life can switch death rates to a lower, healthier trajectory."