If I'm in adjustment phase, I'll use start with 36 or 48 or 72 hr fast... depending on comfort level. Any fast is ok... 12 hours is fine.... longer is better. After the long fast transition to basically eating once every 24 hrs, so, once a day. Meals are thin on carbs but with periodic fasting can basically eat whatever you want. then on particular days throw in another 24 hr fast about once a week. I do NOT do calorie counting, tape measure... etc... just stick diligently to a certain eating routine. That small tweak will boost your energy level, regulate your blood sugar, and the ancillary effect of basically losing weight. Btw... during fasts... continue to drink plenty of water, as long as you stay hydrated and your blood sugar is under control your body slowly starts to adjust to this and then you're on auto pilot.
The benefits are many. Increased energy, less mental fog, weight loss... especially the energy... feel about 10 years younger. Physical flexibility also increases markably... also just _feel_ better overall. Can't recommend it highly enough and it really is very, very simple.
If you have doubts about this, consult with a nutritionist first. NOT a physician, a licensed nutritionist. I found medical doctors next to illiterate on eating and the effects of eating / periodic fasting etc and the effects on physiology.
Cheers!