The Economist discusses recent research into calorie restriction, suggesting that even small reductions in calorie intake have potentially large effects on an organism. "Their [study] suggests that significant gains in longevity might be made by a mere 5% reduction in calorie intake. The study was done on mice rather than people. But the ubiquity of previous calorie-restriction results suggests the same outcome might well occur in other species, possibly including humans. However, you would have to fast on alternate days." Full-press calorie restriction can only extend healthy life span by 30% or so in mice, so my definition of "significant" may be different - but still, interesting research.
Link: http://www.economist.com/science/displayStory.cfm?story_id=3809652