It is still to be proved whether or not intermittent fasting improves the lifespan of humans, but mice do live up to twice as long when they are fasted on little calories and high nutrient dense foods.
You probably already know that there are several variations of the intermittent fasting approach including 16/8 where you fast for 16 hrs and eat during the 8 hour window (14-15 hr fast for women). How do you know which method is for you? You cannot know unless you have had the properly laboratory tests done, but detailed health consultation so that the practitioner can put it all together. If a patient of mine has blood sugar issues, or food allergies or any amount of inflammation for example, then they may need a certain length of fasting to cover the organs that are in need of a physiological-rest. So I recommend that anyone serious about intermittent fasting have a full blood panel done that is nutritionally interpreted comparing your results not to men and women your age, but to health men and women your age - different standard of health equals different health potential.
I have seen dozens of patients who were well intentioned that performed intermittent fasting that triggered their thyroid to slow town, that promoted inflammation by stressing the body and disrupted hormone levels to say the least.