Hi and thanks for using the forum.
The most common reason for the dizzyness that you have described is dehydration. Since you have recently changed your diet and lost weight, it is possible that you have not been drinking enough. The next possibility is that you are not taking in enough calories and therefore feeling weak. At 14, your body is growing and changing a lot and your metabolism tends to pick up greatly. You should discuss this with your pediatrician. He/she can help you figure out how many calories you need a day as well as give you information for healthy food choices. It is possible that you could have an inner ear infection and that too can be ruled out by your pediatrician. I hope this helps. Good luck.
Bridget
Due to experiencing the symptoms you listed, I would think it could be an inner ear infection. I had it real bad last year...Though I felt absolutely nothing wrong with my ears, a CT scan revealed that I had a minor inflammation way down in my ear, but for the most part, the emergency room doctor explained to me that there may be something that is microscopic to the eye, that is blocking blood flow through the ear canal, which causes vertigo "dizziness" headaches, nausea, and imbalance.
They sell a medicine called "meclizien" over the counter that you might want to try. It is "to me", the closes thing to promethizine, which my doctor prescribed me...See if it helps with the dizzy spells...Other than that, see your pediatrician! I'm sure they will get to the bottom of this!
Good luck!
Were you trying to lose too much weight too fast by semi-fasting?