Have you started heavy exercise and diet all of a sudden? If so, that may be the reason for your dizziness
since there could be a significant change in the body's metabolism
I suggest you not to go for a crash diet
and do heavy exercise, rather have a slow and steady approach and then start increasing it gradually so that your body copes up.
For beginners, start by taking a slow 15 mins walk in the morning and over a week, increase both the duration and speed till you walk for 30 mins briskly (with sweating).
As for diet, avoid rice and milk products. That itself will give good results.
All the best.