Every time I have tried to fast in the past it has completely fk'd my metabolism for at least a few weeks sure I drop a lot of lbs over the fast period but something about my body chemistry make me pile on weight like no tomorrow after I stop fasting (maybe my intervals are too long or two short, my understanding of IF is shaky at best). that being said I know that this method has and does work for a few guys I know.
What I do is sort of similar in spirit. 3 weeks of high intensity training (strength training and high intensity cardio) combined with a very clean diet, followed with a week of moderate intensity training (endurance training, plyometrics, low intensity cardio) with a more relaxed diet. Not a nutritionist or personal trainer by any means, but this has worked for me pretty well over the past year and a half I've been doing it. I started at 215 lbs after my senior year of high school (summer 2011), I was down to 150 over the summer (2012) but I was pretty low on muscle mass too. Right now I'm hovering around 165 and feeling a lot fitter. My lifting IRM's have roughly doubled since I started: Bench 180, Deadlift 300, Squat 210; I'm working on breaking out of a plateau right now but other than the past month I've seen slow steady increases in strength, endurance (cardiovascular and muscular), increase in muscle mass, and visual decrease in body fat (haven't had it accurately measured but I'm around 12%, at a conservative estimate).
When you boil it all down the bare bones of getting in better shape are irrefutably a decent diet and physical activity. No matter what approach you take It's going to take a lot of hard work and dedication, but the end result is well worth it in my opinion. Your biggest obstacle is your own mind.