I've dabbled with caloric restriction before for brief periods of time. I found that my body adjusted pretty quickly to it in a metabolic sense and the only real issue (and the reason I dabbled but never became a real adherent) was appetite, which I suspect will eventually be solvable via pharmacological means.

Intermittent caloric restriction is also showing promise. You don't have to starve yourself daily -- just a couple of times a week -- to show some of the same benefits. Perhaps not to the same degree, but far more comfortably.

Why speculate when we already have some data on activity levels under CR?

http://en.wikipedia.org/wiki/Calorie_restriction#Activity_le...

Very interesting!

>Laboratory rodents placed on a CR diet tend to exhibit increased activity levels (particularly when provided with exercise equipment) at feeding time. Monkeys undergoing CR also appear more restless immediately before and after meals.[62] Despite this brief daily period of increased activity overall activity is no higher in CR than AL animals in youth after an initial period of adaptation to the diet.[63] On the other hand, CR has been found to retard the decline in activity that occurs during normal aging: in one study, animals on a conventional diet "showed little activity" by early middle age, while those on CR "were observed to run around the cage and climb onto and hang from the wire cage tops throughout their life spans. In fact, the longest surviving [CR] mouse was observed hanging from the top of his cage only 3 days before he became moribund."

Just thinking all futurism here, but it could be useful in the case where we don't need as much physical activity but rely more on thinking, or if we have things pretty automated and just need to wait for things that take a long time.