The effort needed varies between individuals. You can't deny the extreme changes in short periods of time with some good responders.
There is NO ONE who will look like a Kevin Levrone(or any other IFBB bodybuilder) overnight. These types of physical changes require YEARS of hardcore training, dieting, and of course, anabolic steroids.
To put it in to perspective, in the last 10 years, I have not taken off more than 7 days COMPLETELY from the gym--EVER, and these occasions that I did were extremely rare. For the past 10 years, every 2-3 hours, I am consuming 40-60 grams of protein. For the past 10 years, I have been training in the gym at least 4-6 times per week, for at least 60-90 minutes. This is a lifestyle for me and although I will admit that I could have NEVER looked like I do naturally, it has taken me QUITE a long time to get here, and it's the same for any IFBB bodybuilder but even more so.