Think of it this way, when you "CRASH" a car, obviously you are doing damage to it and that car will never be the same. It decreases in value and it may not run as smoothly as before. The same thing happens to your body when you crash diet. You begin to damage your body and you will probably gain the weight right back.
The idea of a crash diet is when one drastically cuts their caloric intake by about 500 calories per day. Women will do this for several reasons. "I need to fit in that perfect wedding dress or I have a hot date in two weeks." For younger girls, there are pressures at school to appear a certain way and in order to be with the "in-crowd" they feel like they need to lose a few pounds. That is when it gets dangerous because when you start to restrict your body, you lower your immune system and your body start to break down on you.
Here's another example. Your brain uses glucose (carbs) for energy and it's appetite runs at around 400 calories per day. This is just YOUR BRAIN! On a crash diet, your brain will be competing with your body for small amounts of energy that's might be available (remember you've cut your intake by 500 calories). As a result, you may become tired sooner, weak and at times dizzy from not feeding yourself properly. http://www.straighthealth.com:
I had a client that was a healthy size woman when I first started to train her. So, we agreed that reshaping and maintaining was her goal. She stood easily at 5'7" about 130 lbs. Yet, once she really started to get into group training and seeing results, she started to think "skinner" was better. I quickly noticed that she would constantly start to get sick (common cold to a virus), she couldn't sleep at night and I started to notice that she was getting a little too thin. After having a conversation about her eating habits I learned that she had cut her caloric intake by almost 600 and she was NOT replacing the calories lost in her training. She was down a total of 1000 calories per day! YIKES! It was great that she would eat salads and grilled chicken but restricting your body from other nutrients like carbohydrates, healthy fats and sugars your body is definitely in the danger zone. If your body is burning an average of 1800 calories per day and then you throw in cardio/exercise which is another 400-600 calories (depending on body type and exercise) you need to replenish your body with a 2200 calories. That's it!
http://www.myfitnesspal.com. It's an easy way to track your food and you can download it onto your smart phone or sign up online. It's free and easy to navigate! If you are trying to loss weight and you want to do it the right way, there are so many "structured" food plans through Weight Watchers, Jenny Craig, the American Heart Association and the U.S. Department of Agriculture just to name a few. These programs are a great way to educate you on food and portion control to help you lose weight effectively and for good! You can also talk to your doctor, personal trainer or local nutritionist. They should be more than happy to help you get on the right track to a healthier you!