There you stand in front of your bathroom mirror. Chances are, here's how the conversation between you and you goes:
First thing in the morning: "I look awful. Look at those bags! I'm all puffy. Is that a zit? Dang! I'm pathetic."
Second thing in the morning: "Is that muscle? Nope. It's jiggling. Gosh, how'd I get so fat?"
Third thing in the morning: "Does this make me look fat? It must have shrunk in the wash. No, I'm fat. I give up. I'll never get into a size 2/4/6/8/12/20 again."
Given how you're talking to yourself, it's likely you will keep that weight on, along with the puffy eyes and... sorry, that unwelcome zit. At least longer than you would like.
Here's how it works: Whatever you declare as your state of being, is what your mind believes. Especially when you state, "I am." Your mind eats that up as the truth of who you are, and triggers the appropriate neuropeptides to inform the cells of your body to respond in a certain way, and you to act accordingly.
For example, if you repeat to yourself, "I am fat," your mind will hop to and send information to your cells to maintain a "fat" condition. If, however, you repeat to yourself, "I am slimming down," or "I am getting healthier," your mind will, good servant that it is, send information to your cells to conform to "slimming down" or "getting healthier" (assuming that "getting healthier" in your thoughts includes slimming down).
No, this doesn't mean that you can say "I'm slimming down," even as you stuff your face with cronuts, and lose that weight. Because that would be lying to yourself! You don't believe for an instant that you can eat unlimited cronuts and lose weight. If you want your mind and body to take as truth your "I'm slimming down," then you must be truthful with your behavior.
But here's the good part: Once you say to yourself, believing it, "I am slimming down," regardless of your actual current weight, you'll find yourself less inclined to eat that extra cronut -- or two or three. You'll find yourself drawn more often to the veggie aisle than the chips aisle. Or at least easier to pass by the chips aisle as you repeat to yourself: "Um, think not. I'm slimming down."
Why not just cut out the cronuts, you ask? Wouldn't that do it? Maybe. But the mind is very powerful, and you can harness that power to work for you. Just as saying "I'm always sick" or "I always get a bunch of colds over the winter" pretty much guarantees that you will, saying, "I'm so lucky, I hardly ever get a cold" pretty much guarantees that you won't.
Appreciate not only who you are, but who you want to be. That's how we can most easily make positive changes in our lives. Make the "I am" statements you want to be your truth, and repeat them diligently. Your self-evaluation "I am fat" didn't happen because you thought it once. You said that to yourself over and over. Similarly, to implant the new thought "I am slimming down" will require repetition. Given that, your mind and body will slowly conform themselves accordingly. Not overnight (you wish), but certainly over time.
Be mindful of your thoughts. Be consistent with your new, more supportive way of thinking of yourself. Appreciate how beautifully your mind and body work together, and get ready for success!