Periodic fasting and caloric restriction
can add 40-50 (healthy) years to your lifespan.
You can achieve a low-calorie lifestyle in two alternative ways:
(a) regular (continuous) caloric restriction, the same calorie-level every day; or
(b) periodic total-fasting days, with normal calorie-level on other days.

Which of these two approaches is better?

Although regular caloric restriction has been proved to be an effective life-extending technique, it's in fact strongly recommend to choose the alternative approach (periodic fasting).

If you are serious about achieving optimum results by means of caloric restriction, there are several important reasons to choose the periodic fasting method, rather than simply a constant calorie-level each day.