It helps tremendously if you understand what happens to your body when you suddenly cut calories.
It sees an upset homeostasis and it immediately realizes that the new deficit that has been taken has to be replaced immediately.
The easiest way for your body to do this is to grab hold of the nearest food it can find, which is muscle tissue. Readily available, hot to the touch, and expendable.
Think about it.
You lower your metabolism and slow your body by 1000 calories, it's gonna find them somewhere.
Gradual is the answer.
Start out by cutting the garbage first, the the types of carbs, which are usually included in the 'garbage'
Your body isn't going to just automatically adjust to a lower fuel intake. This is why extremely fat people can say "I eat like a bird and I still gain fat"
Yes, they do, and they will. Their bodies have become fat-storing machines. They are still gonna store fat regardless of the intake associated.
If you worked hard for the muscle you've gained, you'd better work just as hard to try and save it while you try to get your body to burn off excess fat.
It's not an easy task. This is why there aren't that many people who are extremely fit. High muscle content and low bodyfat levels.
More often we see either "thin-fatties" or Perma-Bulkers.