Iíve done IF for over a year and I believe it is one of the most valuable tools for health. Turned 40 this year, but with a history of competitive sports (boxing and American football), the mileage is much higher. All my joints hurt (I have been told by a doctor that I have the knees of an 80 year old), multiple surgeries, not to mention taking too many hard shots to the head (Iím a lawyer now, and I can tell that Iím not as quick witted as I had been). Anyway, Iím still in decent shape with fairly low body fat (visible abs). I want to design an IF program that does the best job at rejuvenation/disease prevention, while at the same time keeps me from getting too thin or losing muscle (Iíd actually like to put on 10-15 pounds), but also reducing my body fat further. I have no problem doing IF in any manner. I routinely do 16/8, but also have done 20/4 (lost weight fast that way) and have done 40 hours straight. I would appreciate any thoughts/advice.