"The Beast"
You will find it very useful to think of "The Beast" as an "internal entity" that "wakes-up- when-you-diet- and-makes-you-miserable- until-it-forces-you-off-your-diet".
I think of it as a big stupid shuffling hairy creature that wakes up inside my mind and gobbles up all my will power and good intentions (as a light snack) while it drags me off to its lair (in the kitchen) to get into some serious gluttony.J)
And The Beast always wakes up after a few days on any of the usual diets. At first you can ignore it. But after a short time you must fight it. You usually oppose it with sheer will power, and if you're very strong, you succeed for a while. But eventually, it wins. Why? Because it wears you down. It's a part of your mind that's completely obsessive about food. When it's awake and active it focuses on nothing else. You, on the other hand, need to think about other things from time to time---like your family and your job. So eventually, even if you're very strong, The Beast catches you in an unguarded moment. Then your diet is over and the cheating or bingeing begins.
How does The Beast fight you? First, it initiates a sort of restless "food-seeking" behavior (you may not even notice this consciously, but it's influencing you nonetheless). Then it activates food cravings that are initially mild but always become increasingly stronger. Eventually these cravings get so strong that they dominate your conscious thoughts for most of each day. When this stage is reached, very few people can continue to resist eating.
Second, while The Beast is doing these things, it's also slowing down your metabolism so that now you not only feel hungry, grouchy and depressed but you're also slothful and sluggish---and you're not burning much fat either. No doubt about it---this Beast is one tough cookie (uh... creatureJ).