Caloric restriction is absolutely fascinating in all forms. I think intermittent fasting might be the best-known variant of this, but there are others. All of them cause dramatic changes in the way bodies function, from changing the hormones secreted to changing the form of fuel it uses to run itself (e.g. ketones in low-carb diets instead of glucose).
Caloric restriction has a whole bunch of knock-on effects, any one of which could have a huge impact on health and aging. For example, restricting calories means that you're restricting protein. Most people think of protein as a good thing, but that's what stimulates the hormone IGF-1 to be secreted, which is necessary for growth of all kinds--muscle growth (which is why bodybuilders eat as much protein as possible), but also including cancer.
I've seen research that suggests that cells don't go into "repair mode" in the presence of IGF-1. This is just one example of a possible mechanism that caloric restriction could have a hugely beneficial effect on aging and illness in general.
I have a half-written blog post about this I should push out. I'd love to get some more conversation going around this.