At least for me.

It's long been known that caloric restriction is one means of extending lifespan in lower mammals (e.g., lab rats) and presumably humans as well. It's a tough diet to maintain, though, since most who try it are perpetually hungry. Now there's evidence that most of the benefits can be attained by periodic fasting (alternate days), allowing a normal dietary intake, but at more irregular intervals.

It makes sense that, like many features of civilized (in the literal sense, meaning cities and civilization) lifestyles, regular meals are unhealthy for us, since our ancestors were probably more in a "go hungry until you can chase down the next mastodon, then feast" mode, and evolutionarily adapted to it. So we need to consider not just what we eat (more paleolithic foods, like meat, nuts, fruits and berries and less or no grain) but when we eat it as well, if we want to do what our bodies (are still) evolved to do.

This is good news for me because I'll often go long periods without eating, just because I get busy, and have no need for regularity to my meals. Unfortunately, many (particularly hypoglycemic types) start to feel bad if they go more than a few hours without food. Of course, it's possible that if they change their diets and habit, that they could get used to it as well.

That assumes, of course, that our bodies are designed to live a long time, rather than break down rapidly after childbearing years.

We are not "designed" to break down. That idea -- that we are programmed for self-destruction to get out of the way of the next generation -- is an old wives tale. Nature just doesn't work that way.

Consider that in nature, old age is rarely a cause of death. Starvation, predation, disease, parasitic infection, etc. are much more likely.

How long an animal lives depends on how much of its finite metabolic energy it devotes to repair and maintenance. Mice have short life spans because devoting a lot of energy to repair would be a waste since a mouse has a high probability of ending up as someone's dinner.

The fact that calorie restriction works shows that the amount of metabolic energy spent on repair can be changed. We probably have different "modes" that are set based on environmental factors, like how much food is available.

The late Doctor Walford (the guru of caloric restriction) looked at the alternate day feeding diets, and I believe that he concluded that it increased the chances of certain diseases, although it did actually work.

Real shame Walford didn't get on his own diet a bit earlier in his life really.