Extending lifespan has mixed effects on learning and memory
ScienceDaily (2010-05-19) -- Decreasing the intake of calories and tweaking the activity of the hormone insulin are two methods long known to increase lifespan in a wide range of organisms. In particular, studies have shown that longevity can be extended by reducing activity in the insulin-signaling pathway -- a chain of events through which insulin influences numerous biological processes, including metabolism, stress response and development. Now, biologists have found the first evidence that these mechanisms also have an impact on cognitive function. ... > read full article
I am a dedicated fan of anti-aging research. Perhaps you might even call me a desperate fan. Furthermore, I have even done some mild experimentation with Calorie Restriction diets. Usually during the summer when I'm not swamped with so many tasks that I lose my cool and give in to the desire for eats. I will say that I felt damn good during those time, but I'd be willing to believe my reduced stress level could be in part (or mostly) responsible. But I definitely did lose significant amounts of weight, which probably contributed to the "raised energy level" the caloric restriction types like to talk about. In organism more advanced than roundworms (say, humans), its also true that caloric restriction has its own effect on insulin levels, thus tying it closer to these studies.
Not too surprisingly, both processes tie back to the notorious CREB molecule. CREB pretty much needs to be everywhere cAMP is, and cAMP needs to be everywhere a cell wants to start a signal cascade, and pretty much every cell does that. Okay that might be a major generalization. You want more thought than that? Well then don't ask the guy who took biochemistry on pass/fail (and considers it one of the better choices of his undergraduate career), go read those wikipedia articles I linked to.
The moral? Eat lots of good food while you're young, and then get into CR when you get older. I'd guess between age 25 and 30. I'm a bit more hesitant at this point to say that people should start sticking themselves with insulin unless they're diabetic.