Losing significant weight during the first week or so of beginning the Zone diet is common, and is due to the loss of retained fluid (from your previous way of eating) as you lower insulin into the Zone and achieve hormonal balance. In case the wording of my previous reply to you was confusing, I was not suggesting you need to drop a carbohydrate block, but merely informing that if you have hunger with lightheadedness, it would be the appropriate adjustment to make. I did not include this as a recommendation for you in my sentence that followed (the sentence containing my suggestions for you) precisely because you had not mentioned whether your lightheadedness was accompanied by hunger. The weight loss will soon slow to about a pound a week. You could read or reread a Zone book for a better understanding of this and my suggestions.
One of the principles of the Zone is to adjust if needed based on hunger. Again, I don't know if you had hunger with the lightheadedness, but for more info on adjustments, click on the "Hormonal Adjustment Diagnostic Chart" found at the bottom right of this page: http://www.drsears.com/ZoneResource...fault.aspx