A 48 hour fast once a week is probably akin to what our ancestors experienced. As you go along I'd keep a close watch on nutrition. 48 hours is too much for me. I presently attempt to do all my eating in a 6 or 8 hour window everyday, typically not eating until noon at the earliest. Do you have a weight goal? The weight goal along with a healthy diet and activity would be my focus. Staving off the maladies of age is the overall plan here, being able to continue doing and enjoying the things that make life worth living.