But any time I've ever dieted with the sole goal of calorie restriction, whether it be by 500 calories or by 1500, the same thing has happened. I lose the weight (quickly, because I'm young I suppose), and immediately gain it back upon completion of the diet. Even when the diet doesn't end in a binge. Even when the diet is accepted as "normal," like eating 1500 calories a day. The weight always comes right back.
The only times in my life when I have lost weight and kept it off were when I permanently changed a lifestyle habit. For example, when I got over my ED, I lost weight because I was no longer binging. But it can be small changes much more subtle than that.
According to the WebMD metabolism calculator, a 5'4'', moderately active, 18-year-old female who weighs 130 pounds requires 2,226 calories per day. At 120 lbs., she would burn 2,159 a day. That's a 67 calorie difference. Imagine these two theoretical girls in your head. Doesn't it seem like the heavier girl must eat so much more than the other? It's not true.
If the first girl cut 67 calories out of her day, theoretically, she would eventually weigh 120 lbs. Of course, it would be difficult to monitor your calories that closely, and you would wait a long time. She would need to permanently change her habits, so there would be no need to obsessively keep track of calories. And then, as the weight gradually falls off, it will be gone for good!
FitDay lists 1 tablespoon of mayo has having 98 calories. 2 tablespoons of Ranch dressing have 147, while two tablespoons of honey mustard have 101 (46 calories less) The difference between a Tall Iced Caramel Macchiato and a Grande Iced Caramel Macchiato is exactly 70 calories. (170 vs. 230) Get where I'm going with this?
Cutting 500 calories out of your day is hard to do with small changes. Instead, dieters resort to depriving themselves of their favorite foods. They ignore hunger pangs while thinking "it's only temporary." So when the diet ends, they haven't changed how they think about food or altered their habits at all. They go right back into their old habits. Then, they find themselves dieting again and again.
To prevent this cycle, find the areas in your diet in which you won't mind a little compromise. I'm always here if you'd like to share what you decide.